ci/init-stage2: allow sourcing the job env vars from the CWD

This will make it easier for the b2c jobs to use this script, as I
don't think I should extract the job folder to /.

Signed-off-by: Martin Roukala (né Peres) <martin.roukala@mupuf.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21872>

.gitlab-ci/common/init-stage2.sh

@@ -36,7 +36,9 @@ BACKGROUND_PIDS=
 # Second-stage init, used to set up devices and our job environment before
 # running tests.
 
-. /set-job-env-vars.sh
+for path in '/set-job-env-vars.sh' './set-job-env-vars.sh'; do
+    [ -f "$path" ] && source "$path"
+done
 . "$SCRIPTS_DIR"/setup-test-env.sh
 
 set -ex