cmd/compile: run TestLogOpt for riscv64 on amd64
cmd/compile: run TestLogOpt for riscv64 on amd64

Run TestLogOpt for riscv64 on amd64, as is done for other architectures.
This would have caught the test failure on riscv64 introduced in
47ade08141b23cfeafed92943e16012d5dc5eb8b.

Change-Id: If29dea2ef383b087154d046728f6d1c96811f5a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/227806
Run-TryBot: Joel Sing <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@sing.id.au>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: David Chase <ae171625adc8645b8b79b7e405a6da5aba5341e0@google.com>

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