CMake will not link object files

I can compile and run my program just fine with a two step process. First compile main without linking g++ -std=c++11 -I/opt/googleapis/gens -c -o main.o main.cpp then link with object files in an archive g++ main.o googleapis.ar 'pkg-config --libs grpc++ grpc' -lgrpc++_reflection -lprotobuf -lpthread -ldl. This works pretty well. I've been trying to do the same thing in CMake but nothing I try seems to work. I thought adding the object files to add_executable would work.

cmake_minimum_required(VERSION 3.6)
project(api)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

find_package(PkgConfig REQUIRED)
pkg_check_modules(GRPC++ REQUIRED grpc++)
pkg_check_modules(GRPC REQUIRED grpc)
pkg_check_modules(PROTOBUF REQUIRED protobuf)
include_directories(
        ${GRPC++_INCLUDE_DIRS}
        ${GRPC_INCLUDE_DIRS}
        ${PROTOBUF_INCLUDE_DIRS}
        /opt/googleapis/gens
)
link_directories(
        ${GRPC++_LIBRARY_DIRS}
        ${GRPC_LIBRARY_DIRS}
        ${PROTOBUF_LIBRARY_DIRS}
)
    set(
        GRPC_LIBRARIES
        ${GRPC++_LIBRARIES}
        ${GRPC_LIBRARIES}
        ${PROTBUF_LIBRARIES}
        pthread
        dl
        protobuf
        grpc++_reflection
     )

     file(GLOB MYFILES /opt/googleapi/gens/*.o)

      set(SOURCE_FILES
        parse_arguments.cc
        parse_arguments.h
        streaming_transcribe.cc
        streaming_transcribe_singlethread.cc
        transcribe.cc)

       add_executable(api ${SOURCE_FILES} ${MYFILES})
       target_link_libraries(api ${GRPC_LIBRARIES})