info: shorten __FILE__ on all platforms
info: shorten __FILE__ on all platforms

This is useful not only for MSVC, but also with gcc/Linux
when doing cross-compilation builds and out-of-tree builds.

https://bugzilla.gnome.org/show_bug.cgi?id=745213

jpxiong/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,centricular/gstreamer,jpxiong/gstreamer,centricular/gstreamer,krichter722/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,krichter722/gstreamer,mparis/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,mparis/gstreamer,mparis/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,mparis/gstreamer