Mk/Uses/ninja.mk: Add support for devel/samurai (D29353)

Samurai is a Ninja-compatible build tool with fewer dependencies
than Ninja. Hook it to the framework via a new NINJA_DEFAULT.

This also adds %p to NINJA_STATUS to make Ninja or Samurai print
the percentage of completed jobs to make it easier to eyeball how
much of the build is done.

PR: 254678
Exp-run by: antoine