ccache

USE flags

• doc - Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
• redis - Enable Redis backend for storage via dev-libs/hiredis
• static-c++ - Avoid dynamic dependency on gcc's libstdc++.
• test - Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
• verify-sig - Verify upstream signatures on distfiles