RFR: 8269760: idea.sh should not invoke cygpath directly

[Jorn Vernee]

>From the JBS issue:

Currently idea.sh checks if `CYGPATH` is set, and then continues by invoking `cygpath` directly.

This doesn't work if `CYGPATH` is not actually set to `cygpath`, but to something else, such as `wslpath`.

Instead of invoking `cygpath` directly, the value of the `CYGPATH` variable should be used.

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Depends on: https://git.openjdk.java.net/jdk/pull/4654

Commit messages:
 - use CYGPATH variable instead of calling cygpath directly

Changes: https://git.openjdk.java.net/jdk/pull/4655/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4655&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269760
  Stats: 10 lines in 1 file changed: 0 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4655.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4655/head:pull/4655

PR: https://git.openjdk.java.net/jdk/pull/4655