[11u] RFR (S): 8250876: Fix issues with cross-compile on macos

[Hohensee, Paul]

Please review this backport to allow cross-compiles for macOS aarch64 builds. Patch has already been backported to 15u.

Original issue: https://bugs.openjdk.java.net/browse/JDK-8250876
Original patch: https://hg.openjdk.java.net/jdk/jdk/rev/64490f533d62
11u webrev: http://cr.openjdk.java.net/~phh/8250876/webrev.11u.00/

The patch to toolchain.m4 required changing macros with a UTIL prefix to use a BASIC prefix. Otherwise clean.

Tested by building on x64 macOS with Xcode 12.

Thanks,
Paul