Add back grpc fix for ar -M for bundling dependencies together

Author: raulcd

cpp/cmake_modules/ThirdpartyToolchain.cmake

@@ -3279,14 +3279,33 @@ function(build_grpc)
     endforeach()
   endif()
 
+  # ar -M rejects with the "libgrpc++.a" filename because "+" is a line
+  # continuation character in MRI scripts, so we have to create a copy of the
+  # static lib with a different name that we will bundle later
+  set(GRPC_STATIC_LIBRARY_GRPCPP_FOR_AR
+      "${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}grpcpp${CMAKE_STATIC_LIBRARY_SUFFIX}"
+  )
+  add_custom_command(OUTPUT ${GRPC_STATIC_LIBRARY_GRPCPP_FOR_AR}
+                     COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_FILE:gRPC::grpc++>
+                             ${GRPC_STATIC_LIBRARY_GRPCPP_FOR_AR}
+                     DEPENDS gRPC::grpc++)
+  add_library(gRPC::grpcpp_for_bundling STATIC IMPORTED)
+  set_target_properties(gRPC::grpcpp_for_bundling
+                        PROPERTIES IMPORTED_LOCATION
+                                   "${GRPC_STATIC_LIBRARY_GRPCPP_FOR_AR}")
+
+  set_source_files_properties("${GRPC_STATIC_LIBRARY_GRPCPP_FOR_AR}" PROPERTIES GENERATED
+                                                                                TRUE)
+  add_custom_target(grpc_copy_grpc++ ALL DEPENDS "${GRPC_STATIC_LIBRARY_GRPCPP_FOR_AR}")
+  add_dependencies(gRPC::grpcpp_for_bundling grpc_copy_grpc++)
+
   # Add gRPC libraries to bundled static libs.
   list(APPEND
        ARROW_BUNDLED_STATIC_LIBS
        gRPC::address_sorting
        gRPC::gpr
        gRPC::grpc
-       gRPC::grpc++
-       gRPC::grpc++_reflection
+       gRPC::grpcpp_for_bundling
        gRPC::upb)
   set(ARROW_BUNDLED_STATIC_LIBS
       "${ARROW_BUNDLED_STATIC_LIBS}"