[sysprof] build: check for recent GCC with stdatomic.h

[Christian Hergert <chergert src gnome org>]

commit 55b374b8be0b53d6ee7243901dce851abae9fc61
Author: Christian Hergert <chergert redhat com>
Date:   Tue Aug 23 16:11:14 2016 -0700

    build: check for recent GCC with stdatomic.h

 configure.ac |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index a455bfe..ca79143 100644
--- a/configure.ac
+++ b/configure.ac
@@ -99,6 +99,16 @@ AX_CHECK_COMPILE_FLAG([-std=gnu11],
 
 
 dnl ***********************************************************************
+dnl GCC 4.8 supports gnu11, but lacked the stdatomic.h headers.
+dnl ***********************************************************************
+AC_MSG_CHECKING([whether C compiler supports stdatomic.h])
+AC_TRY_LINK([#include <stdatomic.h>],
+            [atomic_thread_fence(memory_order_acquire);atomic_thread_fence(memory_order_seq_cst);],
+           [AC_MSG_RESULT([yes])],
+           [AC_MSG_ERROR([Sysprof requires a C compiler with stdatomic support such as GCC 4.9 or newer])])
+
+
+dnl ***********************************************************************
 dnl Check for required packages
 dnl ***********************************************************************
 m4_define([glib_required_version], [2.44.0])