ci/deqp-runner: unset CC for arm32 cross-compilation

When CC variable is set to /usr/lib/ccache/gcc, the rust
compiler uses this variable when cross-compiling for arm32,
which causes build failure for zstd-sys. So unset the CC
variable when cross-compiling for arm32.

Signed-off-by: Vignesh Raman <vignesh.raman@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29931>

.gitlab-ci/container/build-deqp-runner.sh

@@ -34,6 +34,12 @@ else
 fi
 
 if [[ "$RUST_TARGET" != *-android ]]; then
+    # When CC (/usr/lib/ccache/gcc) variable is set, the rust compiler uses
+    # this variable when cross-compiling arm32 and build fails for zsys-sys.
+    # So unset the CC variable when cross-compiling for arm32.
+    if [ "$RUST_TARGET" = "armv7-unknown-linux-gnueabihf" ]; then
+        unset CC
+    fi
     cargo install --locked  \
         -j ${FDO_CI_CONCURRENT:-4} \
         --root /usr/local \