Fix the CCache cache path. The default in modern CCache
is ~/.cache/ccache.
Use `github.run_id` for cache key timestamp. Previous timestamp
generation emitted a warning about `set-output` being deprecated.
Set policy_max version to 4.0 to avoid error
Compatibility with CMake < 3.5 has been removed from CMake.
Add github workflow to check CMake compatibility for commonly used
versions and the newest ones.
The gcc-11 disappeared from ubuntu-2004. Change gcc-11 os to ubuntu
22.04 where it is available.
Add gcc-13 and gcc-14 which are now available on ubuntu-2404.
Replace ubuntu-18.04 virtual environment with ubuntu-20.04.
Compilation tests for GCC < 7 cannot be done anymore
since ubuntu-20.04 environment does not provide such an
old compilers.
Report event will write json formatted event into report
file.
Include Boost headers as system headers to avoid generating
excessive warnings. Enable extra tests for selected compilers
in actions.
