main/gcc: disable gdc on 32-bit architectures

On 32-bit arches, gdc fails to compile any software with an arithmetic
error. This is a known upstream bug, there is a patch but it is not yet
merged and requires some tinkering to apply cleanly for GCC 12.X.

See:

* dlang/druntime#3383
* https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/36469#note_248077

main/gcc/APKBUILD

@@ -95,11 +95,15 @@ else
 	_builddir="$srcdir/build"
 fi
 
+case "$CARCH" in
 # GDC hasn't been ported to PowerPC
 # See libphobos/configure.tgt in GCC sources for supported targets
 # riscv fails with: error: static assert  "unimplemented"
-case "$CARCH" in
 ppc64le|riscv64)	LANG_D=false ;;
+# GDC does currently not work on 32-bit musl architectures.
+# This is a known upstream issue.
+# See: https://github.com/dlang/druntime/pull/3383
+armhf|armv7|x86)	LANG_D=false ;;
 esac
 
 # libitm has TEXTRELs in ARM build, so disable for now