In __cwd, make sure the given directory is seen as such and not a file

On Unixly platforms, this doesn't matter.  On VMS, it does.
Reviewed-by: NRich Salz <rsalz@openssl.org>

test/testlib/OpenSSL/Test.pm

@@ -87,7 +87,6 @@ sub __cwd;
 sub __apps_file;
 sub __results_file;
 sub __test_log;
-sub __cwd;
 sub __fixup_cmd;
 sub __build_cmd;
 
@@ -607,7 +606,7 @@ sub __test_log {
 }
 
 sub __cwd {
-    my $dir = shift;
+    my $dir = catdir(shift);
     my %opts = @_;
     my $abscurdir = rel2abs(curdir());
     my $absdir = rel2abs($dir);