cmd/nm, runtime/cgo: add cgo support for freebsd/riscv64
Updates #53466
Change-Id: I08ea279c905e265a579b6b3e23aee012165beaee
Reviewed-on: https://go-review.googlesource.com/c/go/+/431658 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Dmitri Goutnik <dgoutnik@gmail.com>