-gz is apparently supported by GCC 5+ and Clang as well.
Improvements
~~~~~~~~~~~~
-- Added support for GCC 9’s `-gz[=type]` option (previously ccache would think
- that “-gz” alone would enable debug information, thus potentially including
- the current directory in the hash).
+- Added support for the `-gz[=type]` compiler option (previously ccache would
+ think that “-gz” alone would enable debug information, thus potentially
+ including the current directory in the hash).
-- Added support for converting paths like “/c/users” into relative paths on
+- Added support for converting paths like “/c/users/...” into relative paths on
Windows.