[msitools] build-sys: Disable -Wbad-function-cast

[Christophe Fergeau <teuf src gnome org>]

commit 92c8e90eae93f13307ef06fa3dd9aa541e61cd59
Author: Christophe Fergeau <cfergeau redhat com>
Date:   Tue Dec 1 10:55:13 2015 +0100

    build-sys: Disable -Wbad-function-cast
    
    g_once_init_enter() seems to trigger it, causing a somehow noisy build.

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 3e23438..359f458 100644
--- a/configure.ac
+++ b/configure.ac
@@ -65,6 +65,7 @@ done
 gl_WARN_ADD([-Wno-sign-compare])
 gl_WARN_ADD([-Wno-unused-parameter])
 gl_WARN_ADD([-Wno-missing-field-initializers])
+gl_WARN_ADD([-Wno-bad-function-cast]) # g_once_init_enter seems to trigger this
 
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])