CI: bump Mesa to 20.3.1

The version we used does not advertise GL_EXT_color_buffer_half_float
with llvmpipe even though the functionality seems to work.

If the extension is not advertised, the future commit
"tests: extend output-damage to GL shadow framebuffer"
will result in a test failure.

Upgrade Mesa, this gets the extension advertised and the test is happy.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

.gitlab-ci.yml

@@ -20,7 +20,7 @@ stages:
   variables:
     FDO_DISTRIBUTION_VERSION: buster
     FDO_DISTRIBUTION_EXEC: 'bash .gitlab-ci/debian-install.sh'
-    FDO_DISTRIBUTION_TAG: '2021-02-15.0'
+    FDO_DISTRIBUTION_TAG: '2021-02-25.0'
 
 
 container_prep:

.gitlab-ci/debian-install.sh

@@ -143,9 +143,9 @@ make install
 cd ../../
 
 apt-get -y --no-install-recommends install $MESA_DEV_PKGS
-git clone --single-branch --branch master --shallow-since='2020-02-15' https://gitlab.freedesktop.org/mesa/mesa.git mesa
+git clone --single-branch --branch 20.3 --shallow-since='2020-12-15' https://gitlab.freedesktop.org/mesa/mesa.git mesa
 cd mesa
-git checkout -b snapshot c7617d8908a970124321ce731b43d5996c3c5775
+git checkout -b snapshot mesa-20.3.1
 meson build -Dauto_features=disabled \
 	-Dgallium-drivers=swrast -Dvulkan-drivers= -Ddri-drivers=
 ninja -C build install