Package agetool gives the tests that run the age command one that reads and
makes post-quantum files (age >= 1.3): the age on PATH when it can, and
otherwise the one go.mod names as a tool, at the version this module links,
which go tool builds into the build cache.
PQ reports whether the age on PATH makes post-quantum keys. The key goes to
stdout and is dropped: age-keygen refuses -o on a file that exists,
/dev/null included, which would make this false on every age.
Path is PATH with an age and age-keygen that make post-quantum keys first
in it: PATH itself when its own do, otherwise the module's tools before it.
It runs go from the working directory, which must be inside this module.