Don't count fallback archives or content files found in subdirs
Simplify version discovery
More cleaning for this, too
Might as well clean here too
Build via podman for more compatible Linux builds

The binary is dynamically linked to libc, so I'm now building on
Debian buster in order to better support more distros.
Don't print a groundcover summary if there are none

Also state that there are none after they've been scanned for.
Give a meaningful error when the cfg file can't be read
Printing the error already gives the ERROR: prefix
This error is worthy of bailing out over
Return the GameCfg we already have, not nil

This avoids a panic in cases these methods would error out, causing
another error because of a nil pointer.
Nothing can be replaced when checking the first data path
Display the program version in the greeting
Prevent tests from spamming files in $HOME/go
Use GOFLAGS for all builds, just not the external linkmode

Also use the -X flag to set the program version based on the git tag.
Actually report on bad paths
Split these into other files