RFR: 8326368: compare.sh -2bins prints ugly errors on Windows

Tue Feb 20 20:06:06 UTC 2024

The logic in the compare script assumes that we compare two directories, and so always have an `$OTHER`. If we are using `-2dirs`, this is not the case, causing `cygpath` and the following `ls` to fail and print error messages about missing paths. These are benign but annoying.

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Commit messages:
 - 8326368: compare.sh -2bins prints ugly errors on Windows

Changes: https://git.openjdk.org/jdk/pull/17936/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17936&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326368
  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/17936.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17936/head:pull/17936

PR: https://git.openjdk.org/jdk/pull/17936