Fix building with FEATURES=distcc (chokes on TMPDIR being set, respect CFLAGS.

(Portage version: 2.2.10/cvs/Linux x86_64, signed Manifest commit with key A792A613)
alpha stable, bug #502704

(Portage version: 2.2.10_p15/cvs/Linux x86_64, signed Manifest commit with key 611FF3AA)