x86_64-linux-gnu and x86_64-linux-gnux32 use different ABIs and objects built for one cannot be used for the other. In order to build and use compiler-rt for x32, we need to treat x32 as a new arch there. This updates the driver to search using the new arch name.
The arch name used here is "x32" to match D99988. If that should turn out to not be specific enough, it could be changed to something like "x86_64_x32".