[sccache] split compilation cache
[sccache] split compilation cache

CircleCI supports cache corruption check upto 500MB. We will downsize
the sccache size to 2GB and split into 4 chunks. The downsizeing is fine
as our current sccache usage does not exceed 2GB.

aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,libra/libra