[libxml2] gitlab-ci: Allow cast-align warnings from clang

[Nick Wellnhofer <nwellnhof src gnome org>]

commit f2392dc464ac6927b2bd59a5e0d10283afbfe5b6
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Fri Sep 9 13:51:58 2022 +0200

    gitlab-ci: Allow cast-align warnings from clang

 .gitlab-ci.yml           | 2 ++
 .gitlab-ci/test_cmake.sh | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d95bf7f8..822f31bb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -125,6 +125,7 @@ cmake:linux:clang:shared:
   variables:
     BUILD_SHARED_LIBS: "ON"
     CC: clang
+    CFLAGS: "-Wno-error=cast-align"
     SUFFIX: linux-clang-shared
 
 cmake:linux:clang:static:
@@ -134,6 +135,7 @@ cmake:linux:clang:static:
   variables:
     BUILD_SHARED_LIBS: "OFF"
     CC: clang
+    CFLAGS: "-Wno-error=cast-align"
     SUFFIX: linux-clang-static
 
 .cmake:mingw:
diff --git a/.gitlab-ci/test_cmake.sh b/.gitlab-ci/test_cmake.sh
index c9b0e031..99c22a8e 100644
--- a/.gitlab-ci/test_cmake.sh
+++ b/.gitlab-ci/test_cmake.sh
@@ -2,10 +2,10 @@
 
 set -e
 
+CFLAGS="-Werror $CFLAGS" \
 cmake "$@" \
     -DBUILD_SHARED_LIBS=$BUILD_SHARED_LIBS \
     -DCMAKE_INSTALL_PREFIX=libxml2-install \
-    -DCMAKE_C_FLAGS='-Werror' \
     -DCMAKE_BUILD_TYPE=RelWithDebInfo \
     -S . -B libxml2-build
 cmake --build libxml2-build --target install