Also look for backtrace() in libexecinfo.
Accepted upstream as part of
https://bugs.freedesktop.org/show_bug.cgi?id=69702


(wiz)

$NetBSD: patch-configure,v 1.3 2014/06/14 21:57:34 wiz Exp $

backtrace() may be in libexecinfo
From
https://bugs.freedesktop.org/attachment.cgi?id=100403
which is part of
https://bugs.freedesktop.org/show_bug.cgi?id=69702

--- configure.orig	2014-06-05 13:56:49.000000000 +0000
+++ configure
@@ -18860,16 +18860,63 @@ if test "x$ac_cv_header_execinfo_h" = xy
   cat >>confdefs.h <<_ACEOF
 #define HAVE_EXECINFO_H 1
 _ACEOF
- for ac_func in backtrace
-do :
-  ac_fn_c_check_func "$LINENO" "backtrace" "ac_cv_func_backtrace"
-if test "x$ac_cv_func_backtrace" = xyes; then :
-  cat >>confdefs.h <<_ACEOF
-#define HAVE_BACKTRACE 1
-_ACEOF
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing backtrace" >&5
+$as_echo_n "checking for library containing backtrace... " >&6; }
+if ${ac_cv_search_backtrace+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
 
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char backtrace ();
+int
+main ()
+{
+return backtrace ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' execinfo; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_backtrace=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if ${ac_cv_search_backtrace+:} false; then :
+  break
 fi
 done
+if ${ac_cv_search_backtrace+:} false; then :
+
+else
+  ac_cv_search_backtrace=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_backtrace" >&5
+$as_echo "$ac_cv_search_backtrace" >&6; }
+ac_res=$ac_cv_search_backtrace
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+
+$as_echo "#define HAVE_BACKTRACE 1" >>confdefs.h
+
+fi
 
 fi