gcc: Disable -Werror

For release branches -Werror is disabled by default, however, for the
development branch of GCC it is enabled.  Make sure that it is always disabled.

source-builder/config/gcc-common-1.cfg

@@ -191,6 +191,7 @@ URL: 	   http://gcc.gnu.org/
     --with-newlib \
     --disable-nls --without-included-gettext \
     --disable-win32-registry \
+    --disable-werror \
     --enable-version-specific-runtime-libs \
     %{?with_lto:--enable-lto}%{!?with_lto:--disable-lto} \
     --enable-newlib-io-c99-formats \