dry-run: don't get confused by '-I' option Fixes automake bug#13760 for non-GNU make implementations that still support the option '-I'. So far, the only such make implementation are FreeBSD (8.x) make and NetBSD (5.x) make. * lib/am/header-vars.am (am__make_dryrun): If a non-GNU make is being used, try to handle the '-I' option in $MAKEFLAGS correctly. For GNU make, that is already done by the proper use of the $MFLAGS variable. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>