cmake: filter not supported C++ compilation flags

Compilation warnings appears for C++ files, that following
options are not valid:
-ffrestanding,
-Wno-format-zero-length
-Wno-main
-fgnu89-inline
-std-gnu99
Added checks to filter out unsupported flags.

Signed-off-by: Jaroslaw Stelter <Jaroslaw.Stelter@intel.com>