sys-devel/gcc: 6.4.0: drop empty uclibc patches

sys-devel/gcc: 6.4.0: drop empty uclibc patches

commit bd758f25 ("toolchain.eclass: isolate 'epatch'
into 'tc_apply_patches'") slightly changed the way
how patches are applied in empty directories:
it started failing to apply patches (to ease catching
mismatch in requested and applied patches).

The change is to drop empty uclibc versioning.

Reported-by: Stephan Litterst
Closes: https://bugs.gentoo.org/698188
Package-Manager: Portage-2.3.76, Repoman-2.3.17
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>