fix lto plugin detection on openbsd

toolchain/gcc/patches/4.7.3/openbsd-lto.patch

@@ -0,0 +1,13 @@
+diff -Nur gcc-4.7.3.orig/gcc/config.host gcc-4.7.3/gcc/config.host
+--- gcc-4.7.3.orig/gcc/config.host	Tue Oct 18 08:14:14 2011
++++ gcc-4.7.3/gcc/config.host	Tue Jan  7 04:33:29 2014
+@@ -292,6 +292,9 @@
+     out_host_hook_obj=host-solaris.o
+     host_xmake_file="${host_xmake_file} x-solaris"
+     ;;
++  *-*-openbsd*)
++    host_lto_plugin_soname=liblto_plugin.so.0.0
++    ;;
+   *-*-linux*)
+     out_host_hook_obj=host-linux.o
+     host_xmake_file="${host_xmake_file} x-linux"