PR go/84484
libgo: add support for riscv64
Patch by Andreas Schwab.
Reviewed-on: https://go-review.googlesource.com/96377
* go.test/go-test.exp (go-set-goarch): Recognize riscv64-*-*.
From-SVN: r257914
Move the architecture-specific settings out of configure.ac into a new
shell script goarch.sh. Use the new script to collect the values for
all architectures to make them available in go/types.
Also fix cmd/vet to pass the right compiler when it calls SizesFor.
This fixes cmd/vet for systems that are not implemented in the gc
toolchain, such as alpha and ia64.
Reviewed-on: https://go-review.googlesource.com/87635
From-SVN: r256655
