[jdk17u-dev] RFR: 8280863: Update build README to reflect that MSYS2 is supported

[George Adams]

On Mon, 11 Jul 2022 09:24:23 GMT, Christoph Langer <clanger at openjdk.org> wrote:

> Hm, I think this doesn't relate to this backport... Here you are backporting [JDK-8280863](https://bugs.openjdk.org/browse/JDK-8280863) which is rather trivial. 😉
Other than that, looks good. Thanks for tackling the backports to enable the new GHA - it's on my list, too.

@RealCLanger my bad, too many backports recently 😂 I've got a branch with the actions changes too so I'll open that once these four have been merged:

- https://github.com/openjdk/jdk17u-dev/pull/540
- https://github.com/openjdk/jdk17u-dev/pull/541
- https://github.com/openjdk/jdk17u-dev/pull/542
- https://github.com/openjdk/jdk17u-dev/pull/543

Would you mind adding the fix request labels for these as I don't have author status yet

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

PR: https://git.openjdk.org/jdk17u-dev/pull/540