CMake Toolchain File for LLVM, using Clang, libc++, lld and LTO

llvm-toolchain.cmake

set(flags "-flto")
set(c_flags "")
set(cxx_flags "-stdlib=libc++")
set(link_flags "-fuse-ld=lld")

set(CMAKE_C_COMPILER clang)
set(CMAKE_CXX_COMPILER clang++)
set(CMAKE_C_FLAGS_INIT "${c_flags} ${flags}")
set(CMAKE_CXX_FLAGS_INIT "${cxx_flags} ${flags}")
set(CMAKE_EXE_LINKER_FLAGS_INIT "${link_flags}")
set(CMAKE_MODULE_LINKER_FLAGS_INIT "${link_flags}")
set(CMAKE_SHARED_LINKER_FLAGS_INIT "${link_flags}")
set(CMAKE_STATIC_LINKER_FLAGS_INIT "${link_flags}")