Using LINK_SPEC to pass rpath to linker

[Kenneth Chiu]

I'd like to install gcc on a machine without root access. To avoid
having to set LD_RUN_PATH or something similar, I'd like to pass rpath
to the linker automatically. It seems that what I need to do is to set
LINK_SPEC somewhere. Where should I set it that will make the most
sense?

Or is there a much better way to set host-specific linker options that
the driver should pass to the linker?