RFR: 8299330: Minor improvements in MSYS2 Workflow handling [v11]

[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. On windows, the bash it uses is also not run properly, which we should address

Julian Waters has updated the pull request incrementally with one additional commit since the last revision:

  Move shell env call to build-windows.yml

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11782/files
  - new: https://git.openjdk.org/jdk/pull/11782/files/f8b96630..8db93e92

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11782&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11782&range=09-10

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 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