RFR: 8326587: Split Link.gmk into a Windows and Unix part [v2]

[Magnus Ihse Bursie]

> There is not much overlap on how linking is done on Windows on one hand, and on all Unix platforms on the other. This makes Link.gmk basically consists of two parts, each in it own half of if statements, and the few common parts are artificially shoehorned in to fit both sides.
> 
> The code will be much clearer if we just split this into two different files.
> 
> Note that this PR slightly collides with JDK-8326583 (https://github.com/openjdk/jdk/pull/17986). Whichever of this goes in first will mean that the other one needs to make some adaptations.

Magnus Ihse Bursie has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:

  8326587: Split Link.gmk into a Windows and Unix part

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Changes: https://git.openjdk.org/jdk/pull/17987/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17987&range=01
  Stats: 668 lines in 13 files changed: 371 ins; 283 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/17987.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17987/head:pull/17987

PR: https://git.openjdk.org/jdk/pull/17987