Consistently use MavenReport#getReportOutputDirectory()

Author: michael-o

src/main/java/org/apache/maven/plugins/checkstyle/AbstractCheckstyleReport.java

@@ -685,7 +685,8 @@ private void initializeXrefTestLocation(CheckstyleReportRenderer renderer) {
     }
 
     private String determineRelativePath(File location) {
-        String relativePath = PathTool.getRelativePath(getOutputDirectory(), location.getAbsolutePath());
+        String relativePath = PathTool.getRelativePath(getReportOutputDirectory().getAbsolutePath(),
+                location.getAbsolutePath());
         if (relativePath == null || relativePath.trim().isEmpty()) {
             relativePath = ".";
         }