Monolithic builds and more

New features:

• Add support for monolithic builds (experimental, VSCode integration not perfect)
• Add make report, closes #26 (closed)
• Add support for ccache secondary storage backend

Fixes:

• VSCode: Use python.defaultInterpreterPath
• Only install distcc when needed and use a mirror, closes #17 (closed)
• Fix wrongly requiring kerberos when running, closes #67 (closed)
• Split P-clean and P/purge targets from others
• VSCode: Fix restructuredtext settings
• Fix warning when cloning a new stack, closes #69 (closed)
• Fix ccache misses because of compiler check

Improvements:

• Do not install external tools
• Remove Brunel from default projects
• Improve staleness checks, fixes #68 (closed)
• Update to LbEnv 2361 stable

Internal changes:

• Hide .env files in python not Makefile
• Improve logging for concurrent commands
• Adapt to deprecated cSpell settings
• Remove telemetry settings that are useless
• Improve lbenv cache hits
• Suppress debug output from some git calls
• Fix extraneous recreation of symlinks
• Improve run and gdb symlink scripts