This patch is not safe for WITH_CCACHE_BUILD support yet as that causes all
ports to depend on devel/ccache. Enabling that patch would then cause the
new devel/libmemcached dependency to require devel/ccache which is a cyclic
dependency. The autoconf dependency also causes issues.
Add a devel/ccache-memcached slave port that would allow a user to use
the ccache+memcached package manually with ports without WITH_CCACHE_BUILD.
This patch comes from https://github.com/ccache/ccache/pull/58 and has been
an ongoing effort over a few years to be merged into the mainline of ccache.
Documenation for it can be found in the MANUAL file at:
/usr/local/share/doc/ccache/MANUAL.txt
Sponsored by: Dell EMC Isilon
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