[libgsystem] build: Check for sys/capability.h existence

[Colin Walters <walters src gnome org>]

commit 867d65c4450dbd4ef7de2a7fd666831569687d4f
Author: Matthias Vogelgesang <matthias vogelgesang gmail com>
Date:   Thu Aug 27 12:06:31 2015 +0200

    build: Check for sys/capability.h existence
    
    sys/capability.h is not installed by default on Ubuntu/Debian, hence it should
    be checked for before compilation.

 configure.ac |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d504c1f..7d3e6a6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -30,6 +30,7 @@ LT_PREREQ([2.2.4])
 LT_INIT([disable-static])
 
 AC_CHECK_HEADER([attr/xattr.h],,[AC_MSG_ERROR([You must have attr/xattr.h from libattr])])
+AC_CHECK_HEADER([sys/capability.h],,[AC_MSG_ERROR([You must have sys/capability.h from libcap])])
 
 PKG_PROG_PKG_CONFIG