Use ccache in github actions

[gavv]

Our CI builds include building third-party dependencies, like speexdsp and pulseaudio, which take time. We change versions and options of dependencies quite rarely. So I think employing ccache on CI can significantly speed up builds.

ccache is already present in all docker images that we use for CI, so all we need is to setup it properly.

Steps:

• modify scripts/ci_checks/docker.sh to bind ~/.ccache inside container to ~/.ccache outside of it
• modify .github/workflows/build.yml to enable caching of ccache directory (e.g. use this or this gh action)
• modify ci scripts to pass --compiler-launcher=ccache option to scons, which will automatically enable ccache for roc and its dependencies

Related docs:

• https://github.com/roc-streaming/roc-toolkit/blob/develop/docs/sphinx/building/scons_options.rst
• https://github.com/roc-streaming/roc-toolkit/blob/develop/docs/sphinx/building/developer_cookbook.rst
• https://github.com/roc-streaming/roc-toolkit/blob/develop/docs/sphinx/development/continuous_integration.rst