test: Do a minimal test to try to build the libcxx std c++ module

test-libcxx-module.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+#
+# Copyright (c) 2024 Martin Storsjo
+#
+# Permission to use, copy, modify, and/or distribute this software for any
+# purpose with or without fee is hereby granted, provided that the above
+# copyright notice and this permission notice appear in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+set -ex
+
+if [ $# -lt 1 ]; then
+    echo $0 prefix
+    exit 1
+fi
+PREFIX="$1"
+PREFIX="$(cd "$PREFIX" && pwd)"
+export PATH=$PREFIX/bin:$PATH
+
+: ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64}}
+
+for arch in $ARCHS; do
+    # TODO: This should ideally use "$CXX -print-file-name=libc++.modules.json", then parse the json to find the relevant cppm file and include directory.
+    $arch-w64-mingw32-clang++ -I$PREFIX/share/libc++/v1 -std=gnu++23 -Wno-reserved-module-identifier -x c++-module -fmodule-output=std.pcm -o std.cppm.obj -c $PREFIX/share/libc++/v1/std.cppm
+    $arch-w64-mingw32-clang++ -I$PREFIX/share/libc++/v1 -std=gnu++23 -Wno-reserved-module-identifier -x c++-module -fmodule-output=std.compat.pcm -fmodule-file=std=std.pcm -o std.compat.cppm.obj -c $PREFIX/share/libc++/v1/std.compat.cppm
+done