Allow proto-path in the proto_library target

tools/protoc_wrapper/protoc_wrapper.py

Index: tools/protoc_wrapper/protoc_wrapper.py
diff --git a/tools/protoc_wrapper/protoc_wrapper.py b/tools/protoc_wrapper/protoc_wrapper.py
index 8eac88409c676381924f822e3d2fe924e696663a..6aa5101e5e9bd6e409f012c68a2bd62df5a43f07 100755
--- a/tools/protoc_wrapper/protoc_wrapper.py
+++ b/tools/protoc_wrapper/protoc_wrapper.py
@@ -74,6 +74,8 @@ def main(argv):
 
   parser.add_argument("--proto-in-dir",
                       help="Base directory with source protos.")
+  parser.add_argument("--proto-path", action="append", default=[],
+                      help="Base directory with imported protos.")
   parser.add_argument("--cc-out-dir",
                       help="Output directory for standard C++ generator.")
   parser.add_argument("--py-out-dir",
@@ -121,6 +123,9 @@ def main(argv):
     ]
 
   protoc_cmd += ["--proto_path", proto_dir]
+  for extra_proto_dir in options.proto_path:
+    protoc_cmd += ["--proto_path", os.path.relpath(extra_proto_dir)]
+
   protoc_cmd += [os.path.join(proto_dir, name) for name in protos]
   ret = subprocess.call(protoc_cmd)
   if ret != 0: