Change git apply patches to cp because third_party is not managed in Paddle repo

Author: velconia

cmake/external/grpc.cmake

@@ -50,7 +50,7 @@ ExternalProject_Add(
     UPDATE_COMMAND  ""
     CONFIGURE_COMMAND ""
     BUILD_IN_SOURCE 1
-    PATCH_COMMAND git apply ${PADDLE_SOURCE_DIR}/patches/grpc/fix_too_early_destory.patch
+    PATCH_COMMAND cp ${PADDLE_SOURCE_DIR}/patches/grpc/grpc_library.h ${GRPC_SOURCES_DIR}/include/grpcpp/impl/codegen/grpc_library.h && cp ${PADDLE_SOURCE_DIR}/patches/grpc/completion_queue.h ${GRPC_SOURCES_DIR}/include/grpcpp/impl/codegen/completion_queue.h
     # NOTE(yuyang18):
     # Disable -Werror, otherwise the compile will fail in MacOS.
     # It seems that we cannot configure that by make command.

patches/grpc/fix_too_early_destory.patch

@@ -325,14 +325,6 @@ def xreader():
             else:
                 yield sample
 
-        assert finish == process_num
-        for w in workers:
-            print('join worker: ', w)
-            print('join worker: ', w.is_alive())
-            w.join()
-            print('join worker: ', w.is_alive())
-        del workers
-
     return xreader