Revert "avoid usage of CMAKE_CXX_COMPILER_FRONTEND_VARIANT and go with pre 3.14 version"

This reverts commit eab545e.

Author: Martin Posch

CMakeLists.txt

@@ -6,7 +6,7 @@ if(NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
 
 # Generated by `boostdep --cmake parser`
 
-cmake_minimum_required(VERSION 3.8...3.20)
+cmake_minimum_required(VERSION 3.14...3.20)
 
 project(boost_parser VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
@@ -30,7 +30,7 @@ endif()
 
 else()
 
-cmake_minimum_required(VERSION 3.8...3.20)
+cmake_minimum_required(VERSION 3.14...3.20)
 project(parse)
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
@@ -41,12 +41,12 @@ set(CXX_STD 17 CACHE STRING "Set to 14, 17, etc., to enable C++14, C++17, etc.")
 message("-- Using -std=c++${CXX_STD}")
 
 # to just check the different frontend flavours we could use the following code
-if (MSVC)
+if (CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "MSVC")
     get_filename_component(CNAME "${CMAKE_CXX_COMPILER}" NAME)
     message(STATUS "Detected MSVC style compiler frontend '" ${CNAME} "'")
     add_definitions(/W3)
     add_compile_options(/Zc:__cplusplus) # not sure, if it necessary for clang-cl
-else()
+elseif (CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU")
     get_filename_component(CNAME "${CMAKE_CXX_COMPILER}" NAME)
     message(STATUS "Detected GNU style compiler frontend '" ${CNAME} "'")
     add_definitions(-Wall)