gitlab-ci: Pull in GCC 9 from Debian testing in x86_test-gl/vk images

The GCC 8 packages from buster are no longer compatible with libc6 from
testing. We could use the GCC 8 packages from testing instead, but this
is easier.

v2:
* Update piglit-quick_gl test results, due to the piglit issue fixed by
  https://gitlab.freedesktop.org/mesa/piglit/-/merge_requests/294

Reviewed-by: Eric Anholt <eric@anholt.net> # v1
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5186>

.gitlab-ci/container/x86_test-gl.sh

@@ -11,8 +11,6 @@ STABLE_EPHEMERAL=" \
       automake \
       ccache \
       cmake \
-      g++ \
-      gcc \
       libgbm-dev \
       libgles2-mesa-dev \
       libpcre3-dev \
@@ -33,6 +31,7 @@ STABLE_EPHEMERAL=" \
       "
 
 TESTING_EPHEMERAL=" \
+      g++ \
       libc6-dev \
       "
 

.gitlab-ci/container/x86_test-vk.sh

@@ -9,8 +9,6 @@ export DEBIAN_FRONTEND=noninteractive
 STABLE_EPHEMERAL=" \
       ccache \
       cmake \
-      g++ \
-      gcc \
       libgbm-dev \
       libgles2-mesa-dev \
       liblz4-dev \
@@ -29,6 +27,7 @@ STABLE_EPHEMERAL=" \
       "
 
 TESTING_EPHEMERAL=" \
+      g++ \
       libc6-dev \
       "