Multi stage docker file

Author: cedricchevalier19

spack/Dockerfile

@@ -1,7 +1,7 @@
-# syntax=docker/dockerfile:1
+# syntax=docker/dockerfile:1.3
 ARG BASEIMAGE=ubuntu:22.04
 
-FROM $BASEIMAGE
+FROM $BASEIMAGE AS base
 
 ARG SPACK_VERSION=0.19.0
 ARG RECIPES_BRANCH=main
@@ -30,21 +30,31 @@ ADD import_signing_key.sh /tmp
 
 RUN --mount=type=secret,id=signingkey,uid=1000 /tmp/import_signing_key.sh /run/secrets/signingkey
 
-RUN --mount=type=cache,target=/buildcache,source=buildcache source /spack/share/spack/setup-env.sh && \
+FROM base AS builder
+
+RUN --mount=type=cache,target=/buildcache source /spack/share/spack/setup-env.sh && \
     spack mirror add cache /buildcache && \
-    spack buildcache update-index -d /buildcache
+    spack buildcache update-index -d /buildcache && \
+    spack buildcache list --allarch
+
+# Populate cache with build tools
+# Uninstall to avoid bad reuse
+RUN  --mount=type=cache,target=/buildcache source /spack/share/spack/setup-env.sh && \
+    spack env create tools --without-view && \
+    spack env activate tools && \
+    spack add cmake autotools && \
+    spack concretize -f && spack install --fail-fast && \
+    spack buildcache create -a -m cache && \
+    spack uninstall --all
 
 # Define and compile an alien environment
-RUN --mount=type=cache,target=/home/user/buildcache,source=buildcache source /spack/share/spack/setup-env.sh && \
+RUN --mount=type=cache,target=/buildcache source /spack/share/spack/setup-env.sh && \
+    spack buildcache update-index -d /buildcache && \
     spack env create alien --without-view && \
     spack env activate alien && \
     spack add alien +hypre+petsc+xml+hdf5+move+ref ginkgo=omp trilinos=omp && \
-    spack concretize -f && spack install --fail-fast
-
-RUN --mount=type=cache,target=/outcache,source=outcache source /spack/share/spack/setup-env.sh && \
-    ls -ld /outcache && \
-    spack env activate alien && \
-    spack buildcache create -a -d /outcache
+    spack concretize -f && spack install --fail-fast && \
+    spack buildcache create -a -m cache
 
 # # Define and compile an arcane environment
 # RUN source /spack/share/spack/setup-env.sh && \
@@ -61,8 +71,8 @@ RUN --mount=type=cache,target=/outcache,source=outcache source /spack/share/spac
 #     spack add arcane ~wrapper~monoembed && \
 #     spack concretize -f && spack install --fail-fast
 
-RUN source /spack/share/spack/setup-env.sh && \
-    spack clean -a
+# RUN source /spack/share/spack/setup-env.sh && \
+#     spack clean -a
 
-USER root
-RUN rm -rf /tmp/* || true
+FROM base AS final
+COPY --from=builder /spack/opt/ /spack/