[JPS build] fix check for non-existing output roots on Windows

'storedNonExistentOutputs' stores system-independent paths so we need to convert slashes to '/' in nonexistentOutputRoots as well, otherwise 'containsAll' check won't work properly (PATH_HASHING_STRATEGY handles case sensitivity only, it doesn't convert file separators), the method may incorrectly return 'true' causing full rebuild of the corresponding target.

This fixes GwtBuilderTest on Windows.

GitOrigin-RevId: d07aa1cc66d91c67bc54e01dbc201c9115ac51d7

jps/jps-builders/src/org/jetbrains/jps/incremental/storage/BuildTargetConfiguration.java

@@ -185,7 +185,7 @@ public class BuildTargetConfiguration {
           }
         }
         if (wasDeleted) {
-          nonexistentOutputRoots.add(outputRoot.getAbsolutePath());
+          nonexistentOutputRoots.add(FileUtil.toSystemIndependentName(outputRoot.getAbsolutePath()));
         }
       }
     }