ci: build a host version of mesa for cross builds

We're about to introduce a hard dependency on OpenCL functions in Iris
& Anv to generate commands. Intel-clc has been modified to generate
serialized NIR.

A number of builders are doing cross builds, so we can't use the
intel-clc built in that cross build. Other builds like ASAN/MSAN also
complain when running the built version of intel-clc because of
uninitialized values in the packaged LLVM libraries from the
x86_64-base image.

To solve those problems we build a host version of intel-clc and use
that binary in the cross build to generate the serialized NIR.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26797>

.gitlab-ci/meson/build.sh

@@ -2,7 +2,7 @@
 # shellcheck disable=SC1003 # works for us now...
 # shellcheck disable=SC2086 # we want word splitting
 
-section_switch meson-configure "meson: configure"
+section_switch meson-cross-file "meson: cross file generate"
 
 set -e
 set -o xtrace
@@ -49,6 +49,38 @@ if [ -n "$CROSS" ]; then
     fi
 fi
 
+if [ -n "$HOST_BUILD_OPTIONS" ]; then
+    section_switch meson-host-configure "meson: host configure"
+
+    # Stash the PKG_CONFIG_LIBDIR so that we can use the base x86_64 image
+    # libraries.
+    tmp_pkg_config_libdir=$PKG_CONFIG_LIBDIR
+    unset PKG_CONFIG_LIBDIR
+
+    # Compile a host version for the few tools we need for a cross build (for
+    # now just intel-clc)
+    rm -rf _host_build
+    meson setup _host_build \
+          --native-file=native.file \
+          -D prefix=/usr \
+          -D libdir=lib \
+          ${HOST_BUILD_OPTIONS}
+
+    pushd _host_build
+
+    section_switch meson-host-build "meson: host build"
+
+    meson configure
+    ninja
+    ninja install
+    popd
+
+    # Restore PKG_CONFIG_LIBDIR
+    if [ -n "$tmp_pkg_config_libdir" ]; then
+        export PKG_CONFIG_LIBDIR=$tmp_pkg_config_libdir
+    fi
+fi
+
 # Only use GNU time if available, not any shell built-in command
 case $CI_JOB_NAME in
     # ASAN leak detection is incompatible with strace
@@ -66,6 +98,8 @@ case $CI_JOB_NAME in
         ;;
 esac
 
+section_switch meson-configure "meson: configure"
+
 rm -rf _build
 meson setup _build \
       --native-file=native.file \