patch 8.1.1637: after running tests and clean the XfakeHOME directory remains

Problem:    After running tests and clean the XfakeHOME directory remains.
Solution:   Use "rm -rf". (Hirohito Higashi)
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index d3c1184..470f41e 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -84,7 +84,7 @@
 RUN_VIM = VIMRUNTIME=$(SCRIPTSOURCE); export VIMRUNTIME; $(VALGRIND) $(VIMPROG) -f $(GUI_FLAG) -u unix.vim $(NO_INITS) -s dotest.in
 
 clean:
-	-rm -rf *.out *.failed *.res *.rej *.orig
+	-rm -rf *.out *.failed *.res *.rej *.orig XfakeHOME Xdir1 Xfind
 	-rm -f opt_test.vim test.log test_result.log messages
 	-rm -f $(RM_ON_RUN) $(RM_ON_START)
 	-rm -f valgrind.*