Fix a makefile bug for gcc is not the default compiler
Fix a makefile bug for gcc is not the default compiler

If no compiler macro is defined and the system only has clang
or icc, the previous implementation will treat clang as gcc and
will set some incorrect parameters. Now fix it.

Signed-off-by: Lv Meng <2df664ee4255226675c7b29e26307ac8da3842dc@intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

zhenyw/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,zhenyw/beignet,freedesktop-unofficial-mirror/beignet,zhenyw/beignet,freedesktop-unofficial-mirror/beignet,freedesktop-unofficial-mirror/beignet,zhenyw/beignet,zhenyw/beignet,wdv4758h/beignet,freedesktop-unofficial-mirror/beignet