Fix finding of pkgsrc/mk/check-portability.awk:

  ERROR: [check-portability.awk] => Found test ... == ...:
  ERROR: [check-portability.awk] configure: if test "x$ac_cv_unspecified_size_last_struct_member" == "xyes"; then :
  ERROR: [check-portability.awk] configure: if test "x$ac_cv_zero_array_size" == "xyes"; then :

  Explanation:
  ===========================================================================
  The "test" command, as well as the "[" command, are not required to know
  the "==" operator. Only a few implementations like bash and some
  versions of ksh support it.

  ...
Merge branch 'jens-mega-patch' of github.com:/tdb/libstatgrab into jens-mega-patch