Add --noblock_for_lock exit code to documentation
The source for this is
Closes
@@ -46,6 +46,7 @@ Bazel execution can result in following exit codes:
- `2` - Command Line Problem, Bad or Illegal flags or command combination, or
Bad Environment Variables. Your command line must be modified.
- `8` - Build Interrupted but we terminated with an orderly shutdown.
+- `9` - The server lock is held and `--noblock_for_lock` was passed.
- `32` - External Environment Failure not on this machine.
- `33` - Bazel ran out of memory and crashed. You need to modify your command line.
