Support SCCACHE_NOCOMPRESS

[Zaczero]

https://man.archlinux.org/man/zstd.1.en perhaps using zstd's pass-through mode would work well here.

I use disk compression and I prefer to store data plainly on disk (centralized compression settings).

[ahartmetz]

Extending the option SCCACHE_CACHE_ZSTD_LEVEL would almost make this trivial, except zstd doesn't seem to support a compression level that means passthrough. Negative compression levels are defined as "fast compression" modes.