vim-patch:8.2.5145: exit test causes spurious valgrind reports

Problem:    Exit test causes spurious valgrind reports.
Solution:   Skip test.  Add CheckNotValgrind.

cf801d4b95

Cherry-pick RunningWithValgrind() from patch 8.2.5136.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/testdir/check.vim

@@ -171,6 +171,14 @@ func CheckNotAsan()
   endif
 endfunc
 
+" Command to check for not running under valgrind
+command CheckNotValgrind call CheckNotValgrind()
+func CheckNotValgrind()
+  if RunningWithValgrind()
+    throw 'Skipped: does not work well with valgrind'
+  endif
+endfunc
+
 " Command to check for X11 based GUI
 command CheckX11BasedGui call CheckX11BasedGui()
 func CheckX11BasedGui()

src/nvim/testdir/shared.vim

@@ -285,6 +285,12 @@ func GetVimCommand(...)
   return cmd
 endfunc
 
+" Return one when it looks like the tests are run with valgrind, which means
+" that everything is much slower.
+func RunningWithValgrind()
+  return GetVimCommand() =~ '\<valgrind\>'
+endfunc
+
 " Get the command to run Vim, with --clean instead of "-u NONE".
 func GetVimCommandClean()
   let cmd = GetVimCommand()

src/nvim/testdir/test_exit.vim

@@ -117,6 +117,7 @@ func Test_exit_error_reading_input()
   CheckNotMSWindows
   " The early exit causes memory not to be freed somehow
   CheckNotAsan
+  CheckNotValgrind
 
   call writefile([":au VimLeave * call writefile(['l = ' .. v:exiting], 'Xtestout')", ":tabnew", "q:"], 'Xscript', 'b')