[jdk17u-dev] RFR: 8296904: Improve handling of macos xcode toolchain

[Christoph Langer]

I had to adapt the configure changes for the new option to the level of code in jdk17u.

Furthermore, I regenerated docs/building.html which brings it in sync with building.md and removes a change that should not have been made when backporting [JDK-8280863](https://bugs.openjdk.org/browse/JDK-8280863).

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Commit messages:
 - Backport 470f3424fcce0e41b75cccdd5e3a56771cd07ff5

Changes: https://git.openjdk.org/jdk17u-dev/pull/931/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=931&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296904
  Stats: 58 lines in 3 files changed: 16 ins; 0 del; 42 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/931.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/931/head:pull/931

PR: https://git.openjdk.org/jdk17u-dev/pull/931