[jdk20] RFR: 8298527: Cygwin's uname -m returns different string than before [v5]

[Christoph Langer]

> `uname -m` returns `.x86_64` after the latest upgread, instead of `x86_64`. Not sure why.
> 
> However, we can handle this in autoconf-config.guess, to unbreak the build.

Christoph Langer has updated the pull request incrementally with one additional commit since the last revision:

  Review suggestions

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

Changes:
  - all: https://git.openjdk.org/jdk20/pull/15/files
  - new: https://git.openjdk.org/jdk20/pull/15/files/92c0f209..37610b15

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk20&pr=15&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk20&pr=15&range=03-04

  Stats: 6 lines in 1 file changed: 1 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk20/pull/15.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/15/head:pull/15

PR: https://git.openjdk.org/jdk20/pull/15