globvar.t: use nm -P for portability

POSIX specifies well defined output for nm -P

This will hopefully run this test on more platforms, including old AIX,
for which nm produces a different output from what the test expected.

Part of #21623

t/porting/globvar.t

@@ -21,16 +21,17 @@ my %skip = map { ("PL_$_", 1) }
 $skip{PL_hash_rand_bits}= $skip{PL_hash_rand_bits_enabled}= 1; # we can be compiled without these, so skip testing them
 $skip{PL_warn_locale}= 1; # we can be compiled without locales, so skip testing them
 
-
-my $trial = "$Config{nm} globals$Config{_o} 2>&1";
+# -P is POSIX and defines an expected format, while the default
+# output will vary from platform to platform
+my $trial = "$Config{nm} -P globals$Config{_o} 2>&1";
 my $yes = `$trial`;
 
 skip_all("Could not run `$trial`") if $?;
 
-my $defined = $^O eq "hpux" ? qr/\|/ : qr/^[0-9a-fA-F]{8,16}\s+[^Uu]\s+_?/m;
+my $defined = qr/\s+[^Uu]\s+/m;
 
 skip_all("Could not spot definition of PL_Yes in output of `$trial`")
-    unless $yes =~ /${defined}PL_Yes/m;
+    unless $yes =~ /^_?PL_Yes${defined}/m;
 
 my %exported;
 open my $fh, '-|', $^X, '-Ilib', './makedef.pl', 'PLATFORM=test'
@@ -47,11 +48,11 @@ close $fh or die "Problem running makedef.pl";
 my %unexported;
 
 foreach my $file (map {$_ . $Config{_o}} qw(globals regcomp)) {
-    open $fh, '-|', $Config{nm}, $file
+    open $fh, '-|', $Config{nm}, "-P", $file
 	or die "Can't run nm $file";
 
     while (<$fh>) {
-	next unless /$defined(PL_\S+)/;
+	next unless /^_?(PL_\S+)${defined}/;
 	if (delete $exported{$1}) {
 	    note("Seen definition of $1");
 	    next;