dry-run: with GNU make, prefer $(MFLAGS) over $(MAKEFLAGS) Fixes automake bug#13760 for GNU make. * lib/am/header-vars.am (am__make_dryrun): If GNU make is being used, rely on the contents of the $(MFLAGS) variable rather than of the $(MAKEFLAGS) to decide whther make is being executed in "dry run" mode. Not only this makes the code possibly faster and less brittle, but also fixes automake bug#13760 (at least when GNU make is in use). * t/make-dryrun.tap: Adjust: some tests that were xfailing now pass. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>