gcc-configure-common.inc: Stop gcc looking at build system paths
There were puzzling failures when you make a force recompile of any gcc
component. The error was in do_configure with cross-compilation badness
being detected in config.log files.
gcc is different in that many of the config.log files are generated during
the do_compile phase. This means this host contamination issue has always
been present but only shows up on a rebuild.
The fix is to force the appropriate configuration variable to "none required"
then gcc won't look in the bad locations.
[YOCTO #2279]
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
