[network-manager-openvpn] build: fix --enable-lto by using gnu build tools

[Thomas Haller <thaller src gnome org>]

commit cfadfab596a95d9cf90e46ce91c4566ce1936d5f
Author: Thomas Haller <thaller redhat com>
Date:   Sun Feb 12 18:05:21 2017 +0100

    build: fix --enable-lto by using gnu build tools

 configure.ac |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index ffae72d..f5edd0f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,6 +12,10 @@ AC_CONFIG_MACRO_DIR([m4])
 
 AC_CONFIG_HEADERS([config.h])
 
+dnl Prefer gcc-* variants; the ones libtool would choose don't work with LTO
+AC_CHECK_TOOLS(AR, [gcc-ar ar], false)
+AC_CHECK_TOOLS(RANLIB, [gcc-ranlib ranlib], :)
+
 dnl
 dnl Require programs
 dnl