[libxml2] Ignore configure backup file created by recent autoreconf too

[Nick Wellnhofer <nwellnhof src gnome org>]

commit e05491ae62e872ce7eab34418bcbad0142172b20
Author: Vadim Zeitlin <vadim zeitlins org>
Date:   Fri Mar 18 19:24:22 2022 +0100

    Ignore configure backup file created by recent autoreconf too
    
    There is currently no way to disable the generation of this annoying
    file, see https://savannah.gnu.org/support/?110417, so just ignore it.

 .gitignore | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitignore b/.gitignore
index ce51efe1..94d0593a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,6 +24,7 @@ config.log
 config.status
 config.sub
 configure
+configure~
 dba100000.xml
 depcomp
 doc/Makefile