According to https://ccache.dev/platform-compiler-language-support.html there is growing support for Windows in ccache. It may be spotty for Visual Studio compilers, but I guess should be better for clang and gcc (BTW also not listed in https://docs.travis-ci.com/user/reference/windows/ as available in the worker).
This should probably cover also automated caching back of the object files, with CCACHE_DIR preferably also resolving to “$HOME/.ccache” as it defaults on Linux/Unix systems.
Overall, sounds exciting to have more test targets available from the common ecosystem! Thanks!