[libxml2] Update .gitignore for Windows

[Nick Wellnhofer <nwellnhof src gnome org>]

commit d1505ef57a30961535235e86352ad118aa8a8d2e
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Mon Oct 9 02:10:11 2017 +0200

    Update .gitignore for Windows

 .gitignore |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/.gitignore b/.gitignore
index abbd024..62cd025 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+*.exe
 *.o
 *.lo
 *.log