patch 9.1.0566: Stop dir in findfile() doesn't work properly w/o trailing slash

Problem:  Stop directory in findfile() doesn't work properly without a
          trailing slash.
Solution: Always use fnamencmp(), not fnamecmp().

related: #15200
related: #15202

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_findfile.vim b/src/testdir/test_findfile.vim
index 311020e..89e583a 100644
--- a/src/testdir/test_findfile.vim
+++ b/src/testdir/test_findfile.vim
@@ -101,11 +101,18 @@
   let l = findfile('bar', ';' . save_dir . '/Xfinddir1/Xdir2/', -1)
   call assert_equal(1, len(l))
   call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+  let l = findfile('bar', ';' . save_dir . '/Xfinddir1/Xdir2', -1)
+  call assert_equal(1, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
 
   let l = findfile('bar', ';' . save_dir . '/Xfinddir1/', -1)
   call assert_equal(2, len(l))
   call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
   call assert_match('.*/Xfinddir1/bar',             l[1])
+  let l = findfile('bar', ';' . save_dir . '/Xfinddir1', -1)
+  call assert_equal(2, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+  call assert_match('.*/Xfinddir1/bar',             l[1])
 
   " Test combined downwards and upwards search from Xdir2/.
   cd ../..