CI: switch to the meson-build.sh helper script

This script does the same thing but has a few more toggles than our
custom script which means we can set everything we need in the
gitlab-ci.yml file and have it DTRT.

Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1317>

.gitlab-ci/check-piglit-results.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+
+set -e
+set -o xtrace
+
+if [[ -z "$MESON_BUILDDIR" ]]; then
+    echo "\$MESON_BUILDDIR not set"
+    exit 1
+fi
+
+check_piglit_results ()
+{
+    local EXPECTED_RESULTS="$MESON_BUILDDIR"/test/piglit-results/$1
+    local DEPENDENCY="$MESON_BUILDDIR"/$2
+
+    if ! test -e $DEPENDENCY; then
+	return
+    fi
+
+    if test -e $EXPECTED_RESULTS; then
+	return
+    fi
+
+    echo Expected $EXPECTED_RESULTS does not exist
+    exit 1
+}
+
+check_piglit_results xephyr-glamor hw/kdrive/ephyr/Xephyr.p/ephyr_glamor.c.o
+check_piglit_results xvfb hw/vfb/Xvfb
+check_piglit_results xwayland hw/xwayland/Xwayland