ccache: disable "-Werror"

mingw-w64-ccache/PKGBUILD

@@ -52,6 +52,8 @@ build() {
       -DBUILD_SHARED_LIBS=ON \
       -DSTATIC_LINK=OFF \
       -DENABLE_TESTING=OFF \
+      -DCCACHE_DEV_MODE=OFF \
+      -DWARNINGS_AS_ERRORS=OFF \
       $([[ ${MSYSTEM_CARCH} == aarch64 ]] && echo "-DENABLE_DOCUMENTATION=OFF") \
       ../${_realname}-${pkgver}