RFR: 8263514: Minor issue in JavacFileManager.SortFiles.REVERSE

[Aleksey Shipilev]

SonarCloud reports the problem in  JavacFileManager.SortFiles.REVERSE definition:
 Neither "Math.abs" nor negation should be used on numbers that could be "MIN_VALUE"

        REVERSE {
            @Override
            public int compare(Path f1, Path f2) {
                return -f1.getFileName().compareTo(f2.getFileName());
            }
        }

Since `compareTo` can technically return `MIN_VALUE`, we cannot simply negate it. Luckily, we can just swap the `f1` and `f2` comparison order to achieve the same effect without exposing us to this corner case.

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Commit messages:
 - 8263514: Minor issue in JavacFileManager.SortFiles.REVERSE

Changes: https://git.openjdk.java.net/jdk/pull/2970/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2970&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263514
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2970.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2970/head:pull/2970

PR: https://git.openjdk.java.net/jdk/pull/2970