ci: Build d3d12 gallium driver in debian-x86_32

Adding d3d12 to this ci build will prevent issues such
as #6708 or fixes like !26363 from happening again in the future.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26447>

.gitlab-ci/container/build-directx-headers.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# shellcheck disable=SC2086 # we want word splitting
+
+# When changing this file, you need to bump the following
+# .gitlab-ci/image-tags.yml tags:
+# DEBIAN_BUILD_TAG
+
+set -ex
+
+git clone https://github.com/microsoft/DirectX-Headers -b v1.711.3-preview --depth 1
+pushd DirectX-Headers
+meson setup build --backend=ninja --buildtype=release -Dbuild-test=false $EXTRA_MESON_ARGS
+meson install -C build
+popd
+rm -rf DirectX-Headers

.gitlab-ci/container/cross_build.sh

@@ -76,6 +76,8 @@ export EXTRA_MESON_ARGS="--cross-file=/cross_file-${arch}.txt -D libdir=lib/${MU
 
 . .gitlab-ci/container/build-wayland.sh
 
+. .gitlab-ci/container/build-directx-headers.sh
+
 apt-get purge -y "${EPHEMERAL[@]}"
 
 . .gitlab-ci/container/container_post_build.sh

.gitlab-ci/container/debian/x86_64_build.sh

@@ -83,12 +83,7 @@ rm -rf $XORGMACROS_VERSION
 
 . .gitlab-ci/container/build-shader-db.sh
 
-git clone https://github.com/microsoft/DirectX-Headers -b v1.711.3-preview --depth 1
-pushd DirectX-Headers
-meson setup build --backend=ninja --buildtype=release -Dbuild-test=false
-meson install -C build
-popd
-rm -rf DirectX-Headers
+. .gitlab-ci/container/build-directx-headers.sh
 
 python3 -m pip install --break-system-packages -r .gitlab-ci/lava/requirements.txt