RFR: 1469: Skara does not build on macOS arm64

[Erik Helin]

Hi all,

please review this patch that adds support for both Linux and macOS AArch64 to `gradlew`. I tested this for macOS/AArch64 but did not have a Linux/AArch64 system available (but it really should work unless I made a typo ��).

Testing:
- [x] Tested locally on macOS/AArch64 using `sh gradlew`
- [x] `sh gradlew test` passes

Thanks,
Erik

-------------

Commit messages:
 - 1469

Changes: https://git.openjdk.java.net/skara/pull/1333/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1333&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1469
  Stats: 17 lines in 2 files changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/1333.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1333/head:pull/1333

PR: https://git.openjdk.java.net/skara/pull/1333