build(mge): set right flags for GNU gold linker via MegEngine#44

CMakeLists.txt

@@ -139,8 +139,8 @@ endif()
 CHECK_CXX_COMPILER_FLAG(-fuse-ld=gold CXX_SUPPORT_GOLD)
 if(CXX_SUPPORT_GOLD AND NOT ANDROID AND NOT APPLE AND NOT MSVC AND NOT WIN32)
     message("-- Using GNU gold linker.")
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fuse-ld=gold")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fuse-ld=gold")
+    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${MGE_COMMON_LD}")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${MGE_COMMON_LD}")
 endif()
 
 option(MGE_WITH_JIT "Build MegEngine with JIT." ON)