RFR: 8299330: Workflows should not install MSYS2 in the JDK's source directory [v10]

[Julian Waters]

> MSYS2 should be more appropriately installed into the runner's tool cache 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 10 additional commits since the last revision:

 - Merge branch 'openjdk:master' into patch-2
 - Install in RUNNER_TOOL_CACHE
 - Merge branch 'openjdk:master' into patch-2
 - Merge branch 'openjdk:master' into patch-2
 - Merge branch 'openjdk:master' into patch-2
 - Merge branch 'openjdk:master' into patch-2
 - 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/937247f0..f8b96630

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11782&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11782&range=08-09

  Stats: 8496 lines in 450 files changed: 4510 ins; 2626 del; 1360 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