app-antivirus/clamav: remove --disable-gcc-vcheck from configure flags.

app-antivirus/clamav: remove --disable-gcc-vcheck from configure flags.

Our ClamAV builds have passed the --disable-gcc-vcheck flag to its
configure script for a while. This is intended to skip a (pointless,
on Gentoo) test for old broken versions of GCC, but accidentally leads
to "-O0" being inserted into the CFLAGS. That in turn causes noticeable
performance degradation.

Since the GCC version check is harmless aside from some wasted time,
it seems the simplest solution here is to drop "--disable-gcc-vcheck"
from the build. This commit adds a new revision of the latest unstable
version that does just that.

Closes: https://bugs.gentoo.org/670828
Package-Manager: Portage-2.3.76, Repoman-2.3.16
Signed-off-by: Michael Orlitzky <mjo@gentoo.org>