fixes #238 cmake automatically use ld.gold for linking

src/runtime/inline/* and pass -Btools/build_system for using gold
otherwise

CMakeLists.txt

@@ -17,6 +17,7 @@ endif()
 
 option(ENABLE_CCACHE "enable caching compiler output" ON)
 option(ENABLE_GIL "threading use GIL" ON)
+option(ENABLE_GOLD "enable the gold linker" ON)
 option(ENABLE_GRWL "threading use GRWL" OFF)
 option(ENABLE_INTEL_JIT_EVENTS "LLVM support for Intel JIT Events API" OFF)
 option(ENABLE_LLVM_DEBUG "LLVM debug symbols" OFF)
@@ -32,6 +33,16 @@ if(ENABLE_CCACHE)
   endif()
 endif()
 
+# automatically use the gold linker if found
+if(ENABLE_GOLD)
+  find_program(GOLD_LINKER ld.gold)
+  if(GOLD_LINKER)
+    message(STATUS "found the gold linker ${GOLD_LINKER}")
+    set(CMAKE_LINKER "${GOLD_LINKER}")
+    set(CMAKE_CXX_LINK_FLAGS "${CMAKE_CXX_LINK_FLAGS} -B${CMAKE_SOURCE_DIR}/tools/build_system")
+  endif()
+endif()
+
 # initial clang flags (set here so they're used when building llvm)
 set(CLANG_FLAGS "-Qunused-arguments -fcolor-diagnostics" CACHE STRING "Clang specific C and CXX flags")
 if("${CMAKE_C_COMPILER_ID}" STREQUAL "Clang")