[8u] RFR (S): 8239053: [8u] clean up undefined-var-template warnings

[Hohensee, Paul]

Please review this backport to 8u to enable Xcode 12 builds. The patch is a subset of the large Xcode cleanup patch for 8182299.

Original JBS issue: https://bugs.openjdk.java.net/browse/JDK-8239053
8u webrev: https://cr.openjdk.java.net/~phh/8239053/webrev.8u.hotspot.00/

This is a private Oracle 8u261 issue, so there is no visible commit to use as a basis for the patch. There are no semantic changes, so very low risk.

Thanks,
Paul