[cmake-developers] Extend CMAKE_<LANG>_FLAGS(_<CONFIG>) from a CMake Toolchain

[Brad King]

On 08/23/2017 11:27 AM, maikel van den Hurk wrote:
> change ... optimisation from O3 (CMake internal setting) to O2.

If you want to change the default flags instead of only adding
(prepending) to them then you need to set all the flags by
setting the cache entry directly.  A toolchain file that wants
such control should be setting all the flags anyway.

-Brad