gcc-5.3/gcc-4.9:replace build path with target path in __FILE__

gcc-5.3/gcc-4.9:replace build path with target path in __FILE__

Similar -fdebug-prefix-map, add option -ffile-prefix-map to map one
directory name (old) to another (new) in __FILE__, __BASE_FILE__and
__builtin_FILE ().

With this patch, it fixes build path issue which caused by __FILE__.
We do not need to use relative path to compile any more.

[YOCTO #7058]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70268

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>