Merge branch 'ps/build-tweaks' into rs/use-strvec-pushv

Merge branch 'ps/build-tweaks' into rs/use-strvec-pushv

The topic moves the coccinelle rules from contrib/ to tools/
directory, breaking merges with this topic.

* ps/build-tweaks:
  meson: precompile "git-compat-util.h"
  meson: compile compatibility sources separately
  git-compat-util.h: move warning infra to prepare for PCHs
  builds: move build scripts into "tools/"
  contrib: move "update-unicode.sh" script into "tools/"
  contrib: move "coverage-diff.sh" script into "tools/"
  contrib: move "coccinelle/" directory into "tools/"
  Introduce new "tools/" directory