.gitlab-ci.d/buildtest.yml: Use -fno-sanitize=function in the clang-system job

The latest version of Clang (version 18 from Fedora 40) now reports
bad function pointer casts as undefined behavior. Unfortunately, we are
still doing this in quite a lot of places in the QEMU code and some of
them are not easy to fix. So for the time being, temporarily switch this
off in the failing clang-system job until all spots in the QEMU sources
have been tackled.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20240601070543.37786-4-thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240603175328.3823123-9-alex.bennee@linaro.org>

.gitlab-ci.d/buildtest.yml

@@ -432,6 +432,7 @@ clang-system:
     IMAGE: fedora
     CONFIGURE_ARGS: --cc=clang --cxx=clang++
       --extra-cflags=-fsanitize=undefined --extra-cflags=-fno-sanitize-recover=undefined
+      --extra-cflags=-fno-sanitize=function
     TARGETS: alpha-softmmu arm-softmmu m68k-softmmu mips64-softmmu s390x-softmmu
     MAKE_CHECK_ARGS: check-qtest check-tcg