Make rav1e cli error more verbose if wasm target for benchmarking

[vibhoothi]

We can try to make the CLI bit more verbose when it is wasm target along with windows error.

Reference: Originally posted by @lu-zero in https://github.com/xiph/rav1e/pull/2451#discussion_r466415656

[englishm]

Hi!

It looks like this issue pertains to this code:

https://github.com/xiph/rav1e/blob/6ca4bc75f68298778807e1ec1fcde384aec17594/src/bin/rav1e.rs#L409-L433

and this code: https://github.com/xiph/rav1e/blob/6ca4bc75f68298778807e1ec1fcde384aec17594/src/bin/rav1e-ch.rs#L420-L444

Do we just need to mention that this lack of support also applies to wasm targets here, or is there more information that we could or should be providing?

I'm looking for ways to contribute and this issue seemed like a decent place to start.

[lu-zero]

if your wasm target supports getrusage it could be reported instead. I'd replace the message with "resource usage report is not supported on this platform" or such.