patch 8.1.2373: cannot build with +popupwin but without +quickfix

Problem:    Cannot build with +popupwin but without +quickfix. (John Marriott)
Solution:   Adjust #ifdefs.
diff --git a/src/testdir/test_makeencoding.vim b/src/testdir/test_makeencoding.vim
index 09d36ea..55b2995 100644
--- a/src/testdir/test_makeencoding.vim
+++ b/src/testdir/test_makeencoding.vim
@@ -1,7 +1,9 @@
 " Tests for 'makeencoding'.
 
 source shared.vim
+source check.vim
 
+CheckFeature quickfix
 let s:python = PythonProg()
 if s:python == ''
   throw 'Skipped: python program missing'