[Unix] Passing extra CMake args
[Unix] Passing extra CMake args

Added support for compiler and linker additional arguments in CMake.
By using CLR_ADDITIONAL_LINKER_FLAGS and CLR_ADDITIONAL_COMPILER_OPTIONS
it's possible to pass toolchain options without changing Makefile.

ruben-ayrapetyan/coreclr,cshung/coreclr,krk/coreclr,wtgodbe/coreclr,cshung/coreclr,mmitche/coreclr,mmitche/coreclr,mmitche/coreclr,yizhang82/coreclr,poizan42/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,ruben-ayrapetyan/coreclr,yizhang82/coreclr,krk/coreclr,poizan42/coreclr,wtgodbe/coreclr,yizhang82/coreclr,krk/coreclr,mmitche/coreclr,wtgodbe/coreclr,mmitche/coreclr,poizan42/coreclr,krk/coreclr,cshung/coreclr,poizan42/coreclr,cshung/coreclr,ruben-ayrapetyan/coreclr,ruben-ayrapetyan/coreclr,krk/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,cshung/coreclr,wtgodbe/coreclr,yizhang82/coreclr,mmitche/coreclr,cshung/coreclr,poizan42/coreclr,yizhang82/coreclr,yizhang82/coreclr,ruben-ayrapetyan/coreclr,poizan42/coreclr