[jdk11u-dev] RFR: 8280863: Update build README to reflect that MSYS2 is supported

Fri Nov 25 11:33:14 UTC 2022

The only diffs are the supported VS versions and the fact that for JDK11u we state that versions older than VS 2017 are likely to be unsupported at some point.

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Commit messages:
 - Backport 204e67a7adedc5ff8ed6dbe1da7aa1397c9beb38

Changes: https://git.openjdk.org/jdk11u-dev/pull/1552/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1552&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8280863
  Stats: 6 lines in 2 files changed: 0 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1552.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1552/head:pull/1552

PR: https://git.openjdk.org/jdk11u-dev/pull/1552