patch 8.2.3579: CI sometimes fails for MinGW

Problem:    CI sometimes fails for MinGW.
Solution:   Use backslashes in HandleSwapExists(). (Christian Brabandt,
            closes #9078)
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index cc45393..cd36839 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -93,7 +93,12 @@
 " REDIR_TEST_TO_NULL has a very permissive SwapExists autocommand which is for
 " the test_name.vim file itself. Replace it here with a more restrictive one,
 " so we still catch mistakes.
-let s:test_script_fname = expand('%')
+if has("win32")
+  " replace any '/' directory separators by '\\'
+  let s:test_script_fname = substitute(expand('%'), '/', '\\', 'g')
+else
+  let s:test_script_fname = expand('%')
+endif
 au! SwapExists * call HandleSwapExists()
 func HandleSwapExists()
   if exists('g:ignoreSwapExists')
diff --git a/src/version.c b/src/version.c
index 9c0f845..2dd061e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3579,
+/**/
     3578,
 /**/
     3577,