Add support for BUILD_NUMBER (temporarily)

Some old scripts still use BUILD_NUMBER instead of the
newer BUILD_ID. The later is the preferred one in new
scripts (no matter both still work).

Once moodlehq/moodle-local_ci#303 is fixed
we'll revert this change, when we have everything working with BUILD_ID.

runner/main/run.sh

@@ -57,6 +57,10 @@ fi
 # BUILD_ID, if not defined use the current PID.
 BUILD_ID="${BUILD_ID:-$$}"
 
+# Always make BUILD_NUMBER available, some old scripts use it.
+# TODO: Remove this once https://github.com/moodlehq/moodle-local_ci/issues/303 is fixed.
+BUILD_NUMBER="${BUILD_ID}"
+
 # Base directory to be shared with some containers that will read/write information there (timing, environment, logs... etc.).
 SHAREDDIR="${WORKSPACE}"/"${BUILD_ID}"