patch 8.2.2035: MS-Windows: some tests may fail

Problem:    MS-Windows: some tests may fail.
Solution:   Avoid test failures. (Yegappan Lakshmanan, closes #7346)

src/testdir/test_functions.vim

@@ -1273,7 +1273,16 @@ endfunc
 func Test_executable_longname()
   CheckMSWindows
 
-  let fname = 'X' . repeat('あ', 200) . '.bat'
+  " Create a temporary .bat file with 205 characters in the name.
+  " Maximum length of a filename (including the path) on MS-Windows is 259
+  " characters.
+  " See https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
+  let len = 259 - getcwd()->len() - 6
+  if len > 200
+    let len = 200
+  endif
+
+  let fname = 'X' . repeat('あ', len) . '.bat'
   call writefile([], fname)
   call assert_equal(1, executable(fname))
   call delete(fname)