Merge branch 'maint'

Merge branch 'maint'

* maint:
  tests: avoid few lingering $MAKE redirections
  tests: avoid '$MAKE' redirections, use 'run_make' instead
  tests: avoid use of redirected 'run_make' invocations
  lint: warn against redirected 'run_make' invocations
  comments: next GNU make release 4.0, not 3.83
  tests: fix a potential spurious failure due to global config.site
  HACKING: it's OK to do testsuite refactoring in a micro version

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>