RFR: 8255703: jaotc: Add Windows+Arm64 support

Fri Oct 30 22:16:09 UTC 2020

Quite bad timing given https://github.com/openjdk/jdk/pull/960 is happening, but I'm gonna publish those changes anyway.

Tests aren't passing yet, that's the current result of `test/hotspot/jtreg:tier1_compiler_aot_jvmci`:
Test results: passed: 120; failed: 22; error: 8

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Commit messages:
 - Graal: Emit clean branch immediate in HotSpotConstantRetrievalOp
 - jaotc: add Windows+Arm64 support

Changes: https://git.openjdk.java.net/jdk/pull/972/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=972&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255703
  Stats: 337 lines in 9 files changed: 258 ins; 70 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/972.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/972/head:pull/972

PR: https://git.openjdk.java.net/jdk/pull/972