ci: Add support for running multiple tests simultaneously

To try this out, start a run like using multiple `--test`
arguments.

ci/run_test_suite.sh \
	--deqp \
	--host-gles \
	--backend vtest-gpu \
	--backend gpu \
	--test TEST1 \
        --test TEST2

Signed-off-by: Robert Foss <robert.foss@collabora.com>

ci/run_test_suite.sh

@@ -37,9 +37,11 @@ parse_input()
    	-t|--test)
          TEST_NAME="$2"
          shift
+         if [ -z "$TMP_TEST_FILE" ]; then
             TMP_TEST_FILE=$(mktemp /tmp/deqp_test.XXXXXX)
-         echo "$TEST_NAME" > "$TMP_TEST_FILE"
             TESTS="$TESTS custom"
+         fi
+         echo "$TEST_NAME" >> "$TMP_TEST_FILE"
          ;;
 
    	-v|--vtest)