RFR: 8299330: Avoid installing MSYS2 in the JDK's source directory [v4]

[Julian Waters]

> MSYS2 should be more appropriately installed into the runner's temporary directory rather than inside the newly checked out repository containing all the JDK's source code, as doing so may interfere with the build process and cause weird corner cases in the submitted actions workflow

Julian Waters has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'openjdk:master' into patch-2
 - Formatting
 - Directory reference
 - Avoid installing MSYS2 in the JDK's source directory

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11782/files
  - new: https://git.openjdk.org/jdk/pull/11782/files/a95188fe..1d1b10cc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11782&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11782&range=02-03

  Stats: 156 lines in 7 files changed: 94 ins; 28 del; 34 mod
  Patch: https://git.openjdk.org/jdk/pull/11782.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11782/head:pull/11782

PR: https://git.openjdk.org/jdk/pull/11782