add ccache by default for GH actions?

[jakoch]

When cpp-devbox is used as a build container on GHA:

• figure out, if a mount for ccache to allow restoring ccache in GH actions make sense
  • https://ccache.dev/manual/4.11.html#_common_options
  • consult gha docs for optimal cache settings?

VOLUME /ccache_folder
ENV CCACHE_DIR=/ccache_folder \
    CCACHE_COMPRESS=TRUE \
    CCACHE_COMPRESSLEVEL=5 \
    CCACHE_MAXSIZE=500M

• then, a user would need to setup the ccache_folder handling in their own GHA workflow like this:
  • mkdir ccache_folder
  • mount it during docker run of the container
    • docker run --env=xy -v pwd/ccache_folder:/ccache_folder /user/project/src make configure