This is what the Clang standalone build does too. And setting this
seems to be required to get the standalone build to work on my Mac.
Reviewed By: #lld-macho, MaskRay, Ericson2314, smeenai
Differential Revision: https://reviews.llvm.org/D120269
include(GNUInstallDirs)
if(LLD_BUILT_STANDALONE)
+ set(CMAKE_CXX_STANDARD 14 CACHE STRING "C++ standard to conform to")
+ set(CMAKE_CXX_STANDARD_REQUIRED YES)
+ set(CMAKE_CXX_EXTENSIONS NO)
+
set(CMAKE_INCLUDE_CURRENT_DIR ON)
# Rely on llvm-config.