m4/gnu-make.m4
[…] has wrong assumptions:
11 # Set GNU_MAKE if we are using a recent-enough version of GNU make.
12
13 # Use --version AND trailing junk, because SGI Make doesn't fail on --version.
14
15 AC_DEFUN([gl_GNU_MAKE],
16 [
17 AM_CONDITIONAL([GNU_MAKE],
18 [${MAKE-make} --version /cannot/make/this >/dev/null 2>&1])
19 ])
(Of course on NetBSD make --version /cannot/make/this
cleanly return a succesfull exit status!)
...and indeed in config.log
we can see:
[...]
GNU_MAKE_FALSE='#'
GNU_MAKE_TRUE=''
[...]