[jdk20] RFR: 8298527: Cygwin's uname -m returns different string than before [v3]

[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:

  Be creative to not show autoconf-config.guess error when we handle it in config.guess

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

Changes:
  - all: https://git.openjdk.org/jdk20/pull/15/files
  - new: https://git.openjdk.org/jdk20/pull/15/files/24b695ac..a37da390

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk20&pr=15&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk20&pr=15&range=01-02

  Stats: 85 lines in 1 file changed: 35 ins; 49 del; 1 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