[jdk11u-dev] RFR: 8326591: New test JmodExcludedFiles.java fails on Windows when --with-external-symbols-in-bundles=public is used

[Sonia Zaldana Calles]

Hi all, 

This PR contains a backport of [43c6f0b5880899b797fab2f851bd35be1c342439](https://github.com/openjdk/jdk/commit/43c6f0b5880899b797fab2f851bd35be1c342439). 

Patch is not clean. Test won't build in 11 because it can't find ```import jdk.internal.util.OperatingSystem```.

This class was introduced in 21 as part of [JDK-8303485](https://bugs.openjdk.org/browse/JDK-8303485).

I've worked around that by removing the dependency to that utility function and checking the operating system with System.getProperty("os.name").

Testing: 
- [x] Modified test case passes 

Thanks!

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

Depends on: https://git.openjdk.org/jdk11u-dev/pull/2609

Commit messages:
 - Backport 43c6f0b5880899b797fab2f851bd35be1c342439

Changes: https://git.openjdk.org/jdk11u-dev/pull/2679/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2679&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326591
  Stats: 48 lines in 1 file changed: 30 ins; 5 del; 13 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2679.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2679/head:pull/2679

PR: https://git.openjdk.org/jdk11u-dev/pull/2679