Reduce the size on disk for logs (#42122)

* Reduce the size on disk for logs

This PR does two things:

1. Store a compressed `spack-build-out.txt.gz`
2. Get rid of phase logs, as they are duplicates of
   `spack-build-out.txt`

The logs are not compressed in the stage dir, so on build failure the
workflow for users is no different.

It's just that on install the logs are rarely used, and if needed, users
can easily `gzip -d` or `zgrep` them.

In the case of GCC installs, the compressed logs are <5% of the original
size, which is typically dozens of MBs.

* get rid of "backwards compat" of file names in stage dirs

0 files changed, 0 insertions, 0 deletions