Add '-no-cache' CLI switch, to disable incremental analysis

- The switch discards the argument provided to '-cache' if any
- Using the switch disables the suggestion to use incremental analysis
- Rule tests use that option to avoid the warning, which clutters build logs
- Refs #946

pmd-test/src/main/java/net/sourceforge/pmd/testframework/RuleTst.java

@@ -260,6 +260,7 @@ public abstract class RuleTst {
         try {
             PMD p = new PMD();
             p.getConfiguration().setDefaultLanguageVersion(languageVersion);
+            p.getConfiguration().setIgnoreIncrementalAnalysis(true);
             if (isUseAuxClasspath) {
                 // configure the "auxclasspath" option for unit testing
                 p.getConfiguration().prependClasspath(".");