stage2: select static/dynamic build via project files instead of configure

Replace the configure-driven static/dynamic selection for stage2 with
explicit cabal project files.

Previously a `--enable-dynamic` autoconf toggle, together with the
`m4/accumulate.m4` helper macros, generated cabal.project.stage2.settings
from a .in template, while the Makefile separately appended
--enable-dynamic to GHC_CONFIGURE_ARGS when DYNAMIC=1. Keeping these two
mechanisms in sync was fragile.

Now the stage2 configuration is split into a shared
cabal.project.stage2.common plus two thin variants that import it:

  - cabal.project.stage2.static  (default; shared: False)
  - cabal.project.stage2.dynamic (shared: True, executable-dynamic: True,
                                  rts +dynamic)

The Makefile selects the project file directly through DYNAMIC_SUFFIX and
the new CABAL_PROJECT_FILE variable, so DYNAMIC=1 picks the dynamic file
without any configure round-trip.

Removed as no longer needed:
  - the --enable-dynamic configure option and its substitution logic
  - cabal.project.stage2.settings(.in) template
  - m4/accumulate.m4

Author: andreabedini

Makefile

@@ -85,18 +85,16 @@ VERBOSE ?= 0
 
 UNAME := $(shell uname)
 
-# If using autoconf feature toggles you can instead run:
-#   ./configure --enable-dynamic --enable-profiling --enable-debug
-# which generates cabal.project.stage2.settings (imported by cabal.project.stage2).
-# The legacy DYNAMIC=1 path still appends flags directly; if both are used the
-# configure-generated settings file (import) and these args should agree.
-#
 # Enable dynamic runtime/linking support when DYNAMIC=1 is passed on the make
-# command line. This will build shared libraries, a dynamic RTS (defining
-# -DDYNAMIC) and allow tests requiring dynamic linking (e.g. plugins-external)
-# to run. The default remains static to keep rebuild cost low.
+# command line. This selects the cabal.project.stage2.dynamic project file
+# (shared libraries, dynamic executables, dynamic RTS) instead of
+# cabal.project.stage2.static, and enables the dynamic-only dist steps below.
+# The default remains static to keep rebuild cost low.
 DYNAMIC ?= 0
 
+# Suffix selecting the static/dynamic stage2 project file (see CABAL_PROJECT_FILE).
+DYNAMIC_SUFFIX := $(if $(filter 1,$(DYNAMIC)),dynamic,static)
+
 # Quiet mode: suppress output unless error (QUIET=1)
 QUIET ?= 0
 
@@ -151,10 +149,6 @@ CABAL_ARGS         ?=
 CC_LINK_OPT         =
 GHC_CONFIGURE_ARGS  =
 
-ifeq ($(DYNAMIC),1)
-GHC_CONFIGURE_ARGS += --enable-dynamic
-endif
-
 GHC_TOOLCHAIN_ARGS  = --disable-ld-override
 
 #
@@ -308,13 +302,18 @@ endef
 #
 # NOTE: Do not pass --with-ar or --with-ld to cabal! it will screw up things
 #
+# Cabal project file for the current stage. stage2 has separate static/dynamic
+# variants selected by DYNAMIC (see DYNAMIC_SUFFIX); all other stages use a
+# single project file.
+CABAL_PROJECT_FILE = cabal.project.$(STAGE)$(if $(filter stage2,$(STAGE)),.$(DYNAMIC_SUFFIX))
+
 define CABAL_BUILD_WITH
 	$(1) \
 		--remote-repo-cache $(call NORMALIZE_FP,$(CURDIR)/$(BUILD_DIR)/packages) \
 		--store-dir $(call NORMALIZE_FP,$(CURDIR)/$(STORE_DIR)) \
 		--logs-dir $(call NORMALIZE_FP,$(CURDIR)/$(LOGS_DIR)) \
 	build \
-		--project-file cabal.project.$(STAGE) \
+		--project-file $(CABAL_PROJECT_FILE) \
 		--builddir $(call NORMALIZE_FP,$(CURDIR)/$(STAGE_DIR)) \
 		$(CABAL_ARGS)
 endef
@@ -330,7 +329,7 @@ define CABAL_INSTALL_STAGE0
 	install \
 		--installdir $(dir $(CABAL)) \
 		--builddir $(call NORMALIZE_FP,$(CURDIR)/$(STAGE_DIR)) \
-		--project-file cabal.project.$(STAGE) \
+		--project-file $(CABAL_PROJECT_FILE) \
 		--overwrite-policy=always --install-method=copy \
 		$(CABAL_ARGS)
 endef
@@ -508,8 +507,7 @@ CONFIGURED_FILES := \
 	libraries/ghc-internal/ghc-internal.cabal \
 	libraries/ghc-experimental/ghc-experimental.cabal \
 	libraries/base/base.cabal \
-	rts/include/ghcversion.h \
-	cabal.project.stage2.settings
+	rts/include/ghcversion.h
 
 # __  __       _         _                       _
 # |  \/  | __ _(_)_ __   | |_ __ _ _ __ __ _  ___| |_
@@ -718,7 +716,7 @@ STAGE2_CABAL_BUILD = \
 
 stage2: STAGE=stage2
 stage2: TARGET_PLATFORM:=$(HOST_PLATFORM)
-stage2: $(GHC1) stable-cabal $(CONFIGURE_SCRIPTS) $(CONFIGURED_FILES) cabal.project.stage2 cabal.project.stage2.settings cabal.project.common libraries/ghc-boot-th-next | stage1
+stage2: $(GHC1) stable-cabal $(CONFIGURE_SCRIPTS) $(CONFIGURED_FILES) cabal.project.stage2.common cabal.project.stage2.static cabal.project.stage2.dynamic cabal.project.common libraries/ghc-boot-th-next | stage1
 	$(call PHASE_START,stage2)
 	$(call LOG,Starting build of $(STAGE))
 

cabal.project.stage2 cabal.project.stage2.commoncabal.project.stage2 renamed to cabal.project.stage2.common

@@ -1,6 +1,5 @@
 -- Configuration common to all stages
 import: cabal.project.common
-import: cabal.project.stage2.settings
 
 -- Disable Hackage, we explicitly include the packages we need.
 active-repositories: :none
@@ -68,8 +67,8 @@ packages:
   https://hackage.haskell.org/package/process-1.6.29.0/process-1.6.29.0.tar.gz
   https://hackage.haskell.org/package/semaphore-compat-1.0.0/semaphore-compat-1.0.0.tar.gz
   https://hackage.haskell.org/package/stm-2.5.3.1/stm-2.5.3.1.tar.gz
-  https://hackage.haskell.org/package/template-haskell-lift-0.1.0.0/template-haskell-lift-0.1.0.0.tar.gz
-  https://hackage.haskell.org/package/template-haskell-quasiquoter-0.1.0.0/template-haskell-quasiquoter-0.1.0.0.tar.gz
+  -- https://hackage.haskell.org/package/template-haskell-lift-0.1.0.0/template-haskell-lift-0.1.0.0.tar.gz
+  -- https://hackage.haskell.org/package/template-haskell-quasiquoter-0.1.0.0/template-haskell-quasiquoter-0.1.0.0.tar.gz
   https://hackage.haskell.org/package/text-2.1.3/text-2.1.3.tar.gz
   https://hackage.haskell.org/package/time-1.15/time-1.15.tar.gz
   https://hackage.haskell.org/package/transformers-0.6.1.2/transformers-0.6.1.2.tar.gz
@@ -82,7 +81,6 @@ packages:
   https://hackage.haskell.org/package/happy-2.1.5/happy-2.1.5.tar.gz
   https://hackage.haskell.org/package/happy-lib-2.1.5/happy-lib-2.1.5.tar.gz
 
--- wip/angerman/compile-less (cross-compilation + local store + recompilation avoidance)
 source-repository-package
   type: git
   location: https://github.com/stable-haskell/Cabal.git
@@ -124,8 +122,6 @@ allow-newer: hsc2hs:*
            , text:*
            , time:*
            , transformers:*
-           , template-haskell-lift:*
-           , template-haskell-quasiquoter:*
            , unix:*
            , xhtml:*
 

cabal.project.stage2.dynamic

@@ -0,0 +1,13 @@
+-- Dynamic stage2 build (DYNAMIC=1).
+--
+-- All shared stage2 configuration lives in cabal.project.stage2.common; this
+-- file only selects shared libraries, dynamic executables and the dynamic RTS.
+-- The Makefile uses this project file when DYNAMIC=1.
+import: cabal.project.stage2.common
+
+package *
+  shared: True
+  executable-dynamic: True
+
+constraints:
+  rts +dynamic

cabal.project.stage2.settings.in

@@ -0,0 +1,10 @@
+-- Static stage2 build (default).
+--
+-- All shared stage2 configuration lives in cabal.project.stage2.common; this
+-- file only selects static libraries. The Makefile uses this project file when
+-- DYNAMIC is not set to 1.
+import: cabal.project.stage2.common
+
+package *
+  shared: False
+  executable-dynamic: False

cabal.project.stage2.static

@@ -27,37 +27,9 @@ AC_SUBST([ProjectPatchLevel2])
 AC_SUBST([Suffix],[""])
 AC_SUBST([SourceRoot],["."])
 
-# --- Feature toggle (dynamic only) for imported project settings ---
-AC_ARG_ENABLE([dynamic],
-        [AS_HELP_STRING([--enable-dynamic],[Build shared libraries and enable dynamic RTS])],
-        [enable_dynamic=$enableval],[enable_dynamic=no])
-
-# Initialize accumulation variables
-ALL_PACKAGES=""
-CONSTRAINTS=""
-
-# Provide defaults first (static)
-APPEND_PKG_FIELD([shared: False])
-APPEND_PKG_FIELD([executable-dynamic: False])
-
-AS_IF([test "x$enable_dynamic" = "xyes"], [
-        # Override (we rebuild list to avoid mixing static+dynamic lines)
-        ALL_PACKAGES=""
-        APPEND_PKG_FIELD([shared: True])
-        APPEND_PKG_FIELD([executable-dynamic: True])
-        APPEND_CONSTRAINT([rts +dynamic])
-])
-
-# Indent with two spaces for substitution blocks (uniform handling)
-ALL_PACKAGES=`printf '%b' "$ALL_PACKAGES"`
-CONSTRAINTS=`printf '%b' "$CONSTRAINTS"`
-ALL_PACKAGES_INDENTED=`printf '%s' "$ALL_PACKAGES" | sed 's/^/  /'`
-CONSTRAINTS_INDENTED=`printf '%s' "$CONSTRAINTS" | sed 's/^/  /'`
-ALL_PACKAGES="$ALL_PACKAGES_INDENTED"
-AS_IF([test "x$CONSTRAINTS" = "x"], [CONSTRAINTS="  -- (none)"], [CONSTRAINTS="$CONSTRAINTS_INDENTED"])
-
-AC_SUBST([ALL_PACKAGES])
-AC_SUBST([CONSTRAINTS])
+# Static vs dynamic stage2 builds are selected by the Makefile choosing between
+# cabal.project.stage2.static and cabal.project.stage2.dynamic (DYNAMIC=1), not
+# by configure. See cabal.project.stage2.common and its variants.
 
 # --- Define Programs ---
 # We don't need to check for CC, MAKE_SET, and others for now, we only want substitution.
@@ -93,7 +65,6 @@ AC_CONFIG_FILES([
     libraries/ghc-experimental/ghc-experimental.cabal
     libraries/base/base.cabal
     rts/include/ghcversion.h
-    cabal.project.stage2.settings
 ])
 
 AC_OUTPUT