Gcc: Speed up autodetection of broken gccs

If a gcc is broken: Do time out earlier and do not try to run it
a second time.

Change-Id: I8742e507c8aaf4b9174848555f057840ee03ad22
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Gcc: Make sure to not add '\n' to output needlessly

Change-Id: I5a5d9cda5aba60cbf20b54934dde3ecdccdd99e3
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Gcc: Sanity check predefined macros

Change-Id: Ib6054d4e3348a39eddfc6b41c3a530f1d4d199f0
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>