+if diff_out_=`exec 2>/dev/null; diff -u "$0" "$0" < /dev/null` \
+ && diff -u Makefile "$0" 2>/dev/null | grep '^[+]#!' >/dev/null; then
+ # diff accepts the -u option and does not (like AIX 7 'diff') produce an
+ # extra space on column 1 of every content line.