fix output file computation for source2source compiler

- in accordance with recent changes

src/main/java/org/jastadd/relast/compiler/RelastSourceToSourceCompiler.java

@@ -30,7 +30,7 @@ public class RelastSourceToSourceCompiler extends RelAstProcessor {
     for (GrammarFile grammarFile : program.getGrammarFileList()) {
       printMessage("Writing output file " + grammarFile.getFileName());
       // TODO decide and document what the file name should be, the full path or a simple name?
-      writeToFile(outputBasePath.resolve(inputBasePath.relativize(Paths.get(grammarFile.getFileName()))), grammarFile.generateAbstractGrammar());
+      writeToFile(outputBasePath.resolve(grammarFile.getFileName()), grammarFile.generateAbstractGrammar());
     }
     return 0;
   }