fixup! Bug 40072: Fix torbrowser-incrementals-nightly-*

Fix a syntax error in previous commit,
695bb8ef.

TBBTestSuite/TestSuite/TorBrowserBuild.pm

@@ -263,7 +263,7 @@ sub make_incrementals {
     }
     foreach my $builddir (path($testsuite->{publish_dir} . '/..')->children) {
         if (-f "$builddir/$test->{publish_dir}/sha256sums-unsigned-build.txt") {
-            symlink("$builddir/$test->{publish_dir}", "$nightlydir/$builddir->basename");
+            symlink("$builddir/$test->{publish_dir}", $nightlydir . '/' . $builddir->basename);
         }
     }
     my @cmd = ('make', $test->{projectname} . '-incrementals-nightly');