direwolf/cmake/modules/FindCompiler.cmake

# Clang or AppleClang (see CMP0025)
if(NOT DEFINED C_CLANG AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  set(C_CLANG 1)
elseif(NOT DEFINED C_GCC AND CMAKE_CXX_COMPILER_ID MATCHES "GNU")
  set(C_GCC 1)
elseif(NOT DEFINED C_MSVC AND CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
  set(C_MSVC 1)
  if(MSVC_VERSION GREATER_EQUAL 1920 AND MSVC_VERSION LESS_EQUAL 1929)
    set(VS2019 ON)
  elseif(MSVC_VERSION GREATER_EQUAL 1910 AND MSVC_VERSION LESS_EQUAL 1919)
    set(VS2017 ON)
  elseif(MSVC_VERSION GREATER 1899 AND MSVC_VERSION LESS 1910)
    set(VS2015 ON)
  endif()
endif()