patch 8.1.0317: Cscope test fails when using shadow directory

Problem:    Cscope test fails when using shadow directory.
Solution:   Resolve symlink in Vim. (James McCoy, closes #3364)
diff --git a/src/testdir/test_cscope.vim b/src/testdir/test_cscope.vim
index 71d5487..63f2c18 100644
--- a/src/testdir/test_cscope.vim
+++ b/src/testdir/test_cscope.vim
@@ -259,7 +259,12 @@
 " Test ":cs add {dir}"  (add the {dir}/cscope.out database)
 func Test_cscope_add_dir()
   call mkdir('Xcscopedir', 'p')
-  call system('cscope -bk -fXcscopedir/cscope.out ../memfile_test.c')
+
+  " Cscope doesn't handle symlinks, so this needs to be resolved in case a
+  " shadow directory is being used.
+  let memfile = resolve('../memfile_test.c')
+  call system('cscope -bk -fXcscopedir/cscope.out ' . memfile)
+
   cs add Xcscopedir
   let a = execute('cscope show')
   let lines = split(a, "\n", 1)