This obsoletes <https://gerrit.libreoffice.org/plugins/gitiles/lode/+/
b82e0a9d26ef4c81046c053ff831dccfc84c56be%5E!> "For linux_gcc_release_64, don't
let ccache strip comments" and fixes ccache for all builds using (recent) GCC.

Change-Id: I5fd20b2565f57073c545fe5d3a9639c2c0583a74
Reviewed-on: https://gerrit.libreoffice.org/63979
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>