[ccache] Multiple directories for CCACHE_DIR?

[Wilson Hong]

Hi ccache,
I am trying to improve ccache build performance by improving cache hit rate. One
thing I wanna try is to have multiple folders specified in CCACHE_DIR. Where
first level is local cache, and second level in LAN NFS, third level on AWS s3.
Ccache will start looking for local ccache first, if not found, then search in
NFS folder and then S3, analogy CPU L1-L2-RAM cache architecture.
I take a look ccache man page: https://ccache.samba.org/manual.html, but still
cannot figure out how to do that. Is that supported in ccache? If not, would be
a good idea to implement that? Any advice is welcome. Thanks!