devel/m4  on solaris :
===> *** No /export/home/pkgbin/distfiles/pkg-vulnerabilities file found,
===> *** skipping vulnerability checks. To fix, install
===> *** the pkgsrc/security/audit-packages package and run
===> *** '/usr/pkg/sbin/download-vulnerability-list'.
===> Configuring for m4-1.4nb1
loading cache ./config.cache
checking for mawk... /usr/bin/nawk
checking for gcc... cc
checking whether we are using GNU C... yes
checking for a BSD compatible install... /usr/ucb/install -c -o root -g root
checking whether /usr/pkg/bin/bmake sets $MAKE... ./configure: bad substitution
*** Error code 1

The problem is with:
if eval "test \"`echo '${'ac_cv_prog_make_${ac_make}_set'+set}'`\"
  = set"; then

where ${ac_make} on a solaris box evaluates to /usr/pkg/bin/bmake instead of
just 'make' or 'bmake', resulting in attempting to evaluate the following
variable:
 ${ac_cv_prog_make_/usr/pkg/bin/bmake_set+set}

Suggestions?