cmd/dist: mark cgo as disabled on linux/riscv64
cmd/dist: mark cgo as disabled on linux/riscv64

cgo is not currently supported on this platform.

Updates #27532 and #36641

Change-Id: I4b35f887e869ebc5c156dd754b1c79897a8c5800
Reviewed-on: https://go-review.googlesource.com/c/go/+/215838
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

nawawi/go,CAFxX/go,cloudflare/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,akutz/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,akutz/go,akutz/go,nawawi/go,golang/go,CAFxX/go,golang/go,nawawi/go,akutz/go,CAFxX/go,golang/go,cloudflare/go,golang/go,akutz/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go,akutz/go,golang/go,nawawi/go,nawawi/go,golang/go,CAFxX/go,cloudflare/go,cloudflare/go,akutz/go,golang/go,akutz/go