Bug 1916426 - Pass our LDFLAGS last to the linker command line cargo invokes r=firefox-build-system-reviewers,sergesanspaille

See llvm/llvm-project#107365 (comment)
for an example of how things can go wrong when they are passed first.

I don't think there was a specific reason for them to have been put
first in the first place.

Differential Revision: https://phabricator.services.mozilla.com/D222899

UltraBlame original commit: f6cff71bfc6cba2b1d37d79fce2cb6b5d0b00852

Author: marco-c

build/cargo-host-linker

@@ -1,3 +1,3 @@
 #!/bin/sh
 # See comment in cargo-linker.
-eval ${MOZ_CARGO_WRAP_HOST_LD} ${MOZ_CARGO_WRAP_HOST_LDFLAGS} '"$@"'
+eval ${MOZ_CARGO_WRAP_HOST_LD} '"$@"' ${MOZ_CARGO_WRAP_HOST_LDFLAGS}

build/cargo-host-linker.bat

@@ -1,3 +1,3 @@
 @echo off
 REM See comment in cargo-linker (without extension)
-%MOZ_CARGO_WRAP_HOST_LD% %MOZ_CARGO_WRAP_HOST_LDFLAGS% %*
+%MOZ_CARGO_WRAP_HOST_LD% %* %MOZ_CARGO_WRAP_HOST_LDFLAGS%

build/cargo-linker

@@ -44,7 +44,7 @@ SANITIZERS = {
 
 use_clang_sanitizer = os.environ.get("MOZ_CLANG_NEWER_THAN_RUSTC_LLVM")
 wrap_ld = os.environ["MOZ_CARGO_WRAP_LD"]
-args = split(os.environ["MOZ_CARGO_WRAP_LDFLAGS"])
+args = []
 for arg in sys.argv[1:]:
     if arg in ["-lc++", "-lstdc++"]:
         wrap_ld = os.environ["MOZ_CARGO_WRAP_LD_CXX"]
@@ -60,6 +60,7 @@ for arg in sys.argv[1:]:
             args.append(f"-fsanitize={SANITIZERS[suffix]}")
             continue
     args.append(arg)
+args.extend(split(os.environ["MOZ_CARGO_WRAP_LDFLAGS"]))
 
 wrap_ld = split(wrap_ld)
 os.execvp(wrap_ld[0], wrap_ld + args)

build/cargo-linker.bat

@@ -1,2 +1,2 @@
 @echo off
-%MOZ_CARGO_WRAP_LD% %MOZ_CARGO_WRAP_LDFLAGS% %*
+%MOZ_CARGO_WRAP_LD% %* %MOZ_CARGO_WRAP_LDFLAGS%