libstdc++ multilib install broken

[Kean Johnston]

Bernardo Innocenti wrote:
> The generated Makefile.in for libstdc++v3/ does not seem
> to be using MULTISUBDIR when installing.

I ran into a similar problem with libffi. The way I got around it was to 
make sure that the top level configure is invoked with 
--enable-multilib. I think that that should be automatic, but it 
currently is not. Phil, if you try that and it works, then it is a good 
data point for rethinking how multilibs are handled for the library 
sub-trees, and how their configure scripts are invoked when doing a 
bootstrap.

Kean