patch 8.0.0420: text garbled when the system encoding differs from 'encoding'

Problem:    When running :make the output may be in the system encoding,
            different from 'encoding'.
Solution:   Add the 'makeencoding' option. (Ken Takata)
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 513fd89..e1ce151 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -170,6 +170,7 @@
 	    test_listlbr.res \
 	    test_listlbr_utf8.res \
 	    test_lua.res \
+	    test_makeencoding.res \
 	    test_man.res \
 	    test_marks.res \
 	    test_matchadd_conceal.res \