RFR: 8267059: Gradle :clean and :apps tasks fail on Windows if ANT_HOME contains spaces

[Michael Strauß]

This PR fixes an issue when building OpenJFX on Windows and command-line arguments contain paths with spaces.

The problem is that on Windows, `ant` is invoked via `cmd`, which leads to quotes being interpreted twice. This can be fixed with the option `cmd /s`, which prevents interpreting quotes on the rest of the command line. The result is as if the rest of the command line had been typed verbatim at the command prompt.

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

Commit messages:
 - Use cmd /s option when building on Windows

Changes: https://git.openjdk.java.net/jfx/pull/499/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=499&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267059
  Stats: 45 lines in 1 file changed: 27 ins; 15 del; 3 mod
  Patch: https://git.openjdk.java.net/jfx/pull/499.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/499/head:pull/499

PR: https://git.openjdk.java.net/jfx/pull/499