Major problems with cross-compiling libstdc++-v3

[Richard Earnshaw <rearnsha at arm dot com>]

It looks as though there has been little or no testing of building 
libstdc++-v3 with cross compilers.  I've already filed two PRs for 
problems I've found while trying to configure the arm-elf target, but it 
wouldn't surprise me if there are more.  Both problems so far are with 
configure containing dependencies on tests that are not run for a 
cross-build or in other odd circumstances; they are not (yet) problems 
with the target missing features -- though I suspect there will be some of 
those later, too.

It doesn't help that if configure fails, it just goes on to the next 
target library, rather than stopping and diagnosing an error.

R.