Do not fail if RBE project is empty.

External developers may use RBE without RBE_instance set.
Autoninja should not fail in this case.

Change-Id: I2dbafded690246132bb0ff1cd080caa0b758b4f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5851434
Auto-Submit: Aleksei Khoroshilov <akhoroshilov@brave.com>
Commit-Queue: Aleksei Khoroshilov <akhoroshilov@brave.com>
Reviewed-by: Fumitoshi Ukai <ukai@google.com>

autoninja.py

@@ -199,13 +199,6 @@ def _main_inner(input_args, build_id, should_collect_logs=False):
         if use_remoteexec:
             if use_reclient:
                 project = _reclient_rbe_project()
-                if not project:
-                    print(
-                        "Can't detect RBE project to use.\n"
-                        "Did you setup properly?\n",
-                        file=sys.stderr,
-                    )
-                    return 1
             elif use_siso and project is None:
                 # siso runs locally if empty project is given
                 # even if use_remoteexec=true is set.