Description: Fix autoconf warning on missing AC_LANG_SOURCE
Author: Peter Blackman <peter@pblackman.plus.com>
Last-Update: 2020-07-09

Index: b/configure.ac
===================================================================
--- a/configure.ac
+++ b/configure.ac
@@ -36,9 +36,9 @@
 if test "${enable_atomic_ops}" = "yes" ; then
 
   AC_MSG_CHECKING([whether $CC knows 32-bit __sync_bool_compare_and_swap()])
-  AC_LANG_CONFTEST([#include <stdint.h>
+  AC_LANG_CONFTEST([AC_LANG_SOURCE[#include <stdint.h>
   int main() { uint32_t a = 4;
-  __sync_bool_compare_and_swap(&a, 4, 5); }])
+  __sync_bool_compare_and_swap(&a, 4, 5); }]])
   $CC conftest.c $CFLAGS -o conftest > /dev/null 2> /dev/null
   ret=$?
   rm -f conftest.o conftest
@@ -50,8 +50,8 @@
   fi
 
   AC_MSG_CHECKING([whether $CC knows 64-bit __sync_bool_compare_and_swap()])
-  AC_LANG_CONFTEST([#include <stdint.h>
-  int main() { uint64_t a = 4; __sync_bool_compare_and_swap(&a, 4, 5); }])
+  AC_LANG_CONFTEST([AC_LANG_SOURCE[#include <stdint.h>
+  int main() { uint64_t a = 4; __sync_bool_compare_and_swap(&a, 4, 5); }]])
   $CC conftest.c $CFLAGS -o conftest > /dev/null 2> /dev/null
   ret=$?
   rm -f conftest.o conftest