configuring gcc 4.6 to use gold for LTO plugin

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

I installed binutils with --enable-gold=default then I configured gcc
4.6-20110520 with the same prefix as the newly installed binutils.

config.log shows:

configure:13814: checking where to find the target ld
configure:13842: result: pre-installed in
/home/wakelj/tools/Linux-x86_64/lto/x86_64-unknown-linux-gnu/bin

and gcc/config.log shows:

configure:21077: checking whether we are using gold
configure:21086: result: yes
configure:21097: checking what linker to use
configure:21122: result:
/home/wakelj/tools/Linux-x86_64/lto/x86_64-unknown-linux-gnu/bin/ld

So it has found the desired binutils and $ld_is_gold=yes, but:

configure:23116: checking linker plugin support
configure:23136: result: no

This is because I don't have an in-tree ld and "ld --version 2>&1 |
fgrep plugin-opt" fails, so $gcc_cv_lto_plugin=no

So will this gcc use a linker plugin?

It looks like I could get it to by adding
--with-plugin-ld=blahblah/ld.bfd but then it uses ld.bfd not gold.

The test in gcc/configure on trunk is completely different and seems
to do what I expected (setting $gcc_cv_lto_plugin=yes based on the
version of ld/gold being used, not on whether grepping for plugin-opt
works)

If I want to use 4.6+LTO+plugin do I need an in-tree gold, or don't use gold?

And if I don't have an in-tree binutils but want gold+LTO+plugin I
need to use 4.7?

Thanks.