patch 8.2.4060: win_execute() slow on systems where getcwd()/chdir() is slow

Problem:    win_execute() is slow on systems where getcwd() or chdir() is
            slow. (Rick Howe)
Solution:   Avoid using getcwd() and chdir() if no local directory is used and
            'acd' is not set. (closes #9504)
diff --git a/src/evalwindow.c b/src/evalwindow.c
index f2d9a0b..a47a0c0 100644
--- a/src/evalwindow.c
+++ b/src/evalwindow.c
@@ -707,13 +707,26 @@
     {
 	pos_T	curpos = wp->w_cursor;
 	char_u	cwd[MAXPATHL];
-	int	cwd_status;
+	int	cwd_status = FAIL;
 #ifdef FEAT_AUTOCHDIR
 	char_u	autocwd[MAXPATHL];
 	int	apply_acd = FALSE;
 #endif
 
-	cwd_status = mch_dirname(cwd, MAXPATHL);
+	// Getting and setting directory can be slow on some systems, only do
+	// this when the current or target window/tab have a local directory or
+	// 'acd' is set.
+	if (curwin != wp
+		&& (curwin->w_localdir != NULL
+		    || wp->w_localdir != NULL
+		    || (curtab != tp
+			&& (curtab->tp_localdir != NULL
+			    || tp->tp_localdir != NULL))
+#ifdef FEAT_AUTOCHDIR
+		    || p_acd
+#endif
+		    ))
+	    cwd_status = mch_dirname(cwd, MAXPATHL);
 
 #ifdef FEAT_AUTOCHDIR
 	// If 'acd' is set, check we are using that directory.  If yes, then