Tests: cache build using ccache

[kdave]

There's support for ccache in GH actions, https://github.com/hendrikmuhs/ccache-action, example https://github.com/KeyviDev/keyvi/blob/master/.github/workflows/keyvi.yml .

Add it to the devel workflow that runs build multiple times. Maybe the cache can be shared among the jobs, maybe not and there would have to be one job doing just the build and the the others reuse the cache.