Post setup step shows help

[Kicer86]

In logs, in post setup step of this action you can see execution of ccache --help which seem a leftover.

[vadz]

There is no ccache --help but I've seen this happen when setting verbose input for the ccache versions too old to have it. The corresponding function should probably check for ccacheKnowsVerbosityFlag before using -v...

[Kicer86]

Just checkout my action output: https://github.com/Kicer86/photobroom/actions/runs/3122990346/jobs/5065306383

[vadz]

Ah, sorry, I hadn't realized that getExecOutput() also shows the output, in addition to returning it. There doesn't seem to be any builtin function in the GitHub toolset to just get the output without showing it, but one could be written, I guess.

Another possibility would be to use ccache -V, get version from the output and compare it with 4. It would still show the version of ccache in the logs, but this would be less annoying and more useful than --help output.