message: CMake: don't override the rest of CMAKE_CXX_FLAGS_*
  Same as
  I wanted to pass custom/have righter control over
  O/-g/-UNDEBUG flags, but that is not possible currently,
  since the per-build-type flags are still being overrided.
  Unless that is intentional of course?
  The alternative, is [for me] to specify custom CMAKE_BUILD_TYPE.
diff: @@ -10,15 +10,15 @@ message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")
  if (MSVC)
  set(CMAKE_CXX_FLAGS "/GL /EHsc /W2 ${CMAKE_CXX_FLAGS}")
  - set(CMAKE_CXX_FLAGS_DEBUG "/Od /Zi")
  - set(CMAKE_CXX_FLAGS_RELEASE "/O2 /Oi /Oy /Zc:inline")
  - set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "/O2 /Oi /Zi")
  + set(CMAKE_CXX_FLAGS_DEBUG "/Od /Zi ${CMAKE_CXX_FLAGS_DEBUG}")
  + set(CMAKE_CXX_FLAGS_RELEASE "/O2 /Oi /Oy /Zc:inline ${CMAKE_CXX_FLAGS_RELEASE}")
  + set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "/O2 /Oi /Zi ${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
  set(CMAKE_EXE_LINKER_FLAGS "/LTCG:INCREMENTAL ${CMAKE_EXE_LINKER_FLAGS}")
  else()
  set(CMAKE_CXX_FLAGS "-Wall -march=native -fPIC ${CMAKE_CXX_FLAGS}")
  - set(CMAKE_CXX_FLAGS_DEBUG "-Werror -g -Og")
  - set(CMAKE_CXX_FLAGS_RELEASE "-O3 -DNDEBUG")
  - set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELEASE} -g")
  + set(CMAKE_CXX_FLAGS_DEBUG "-Werror -g -Og ${CMAKE_CXX_FLAGS_DEBUG}")
  + set(CMAKE_CXX_FLAGS_RELEASE "-O3 -DNDEBUG ${CMAKE_CXX_FLAGS_RELEASE}")
  + set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELEASE} -g ${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
  endif()
  set(CMAKE_CXX_STANDARD 17)
  