[gsound] build: Fix autotools warning

[Tristan Brindle <tbrindle src gnome org>]

commit 6c5e4ef278ded46fca4ff1d9f12cc05891fc525f
Author: Tristan Brindle <t c brindle gmail com>
Date:   Thu Nov 27 00:02:36 2014 +0800

    build: Fix autotools warning
    
    I don't really know what AM_PROG_CC_C_O actually does, but
    autotools seems to want it

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7312164..a3f4997 100644
--- a/configure.ac
+++ b/configure.ac
@@ -9,6 +9,7 @@ AC_CONFIG_HEADERS([config.h])
 AM_MAINTAINER_MODE
 
 AC_PROG_CC
+AM_PROG_CC_C_O
 AM_PROG_VALAC
 
 LT_INIT