[driver] Add configure-time specs

[Paolo Bonzini]

On 12/02/2009 06:07 PM, Nathan Sidwell wrote:
> This patch of Mark's adds a --with-specs=... configure option to gcc.
> This allows you to tune a toolchain build without needing to add or
> adjust various t- fragments or header files. We use it to give fine
> grained control over optimization levels, amongst other things.
>
> built and tested (with and without the config option) on
> i686-pc-linux-gnu. ok?

Sorry for commenting late---how likely is it that the flag includes a 
quote and this breaks the -D option in Makefile.in?

Paolo