+# check version of make
+my @mkver = split /\s+/, `$mk -v`, 4;
+my $valid_mk = 1;
+$mkver[0] =~ /^GNU/ or $valid_mk = 0;
+$mkver[1] =~ /^Make/ or $valid_mk = 0;
+$mkver[2] >= "3.81" or $valid_mk = 0;
+$valid_mk or die "Unsupported version of make found: $mk\n";
+