fix: getrandom target error in risc0 and sp1 workflow

[shariqnaiyer]

What was wrong?

risc0 and sp1 use unsupported targets for getrandom and cause an error in our worflow

How was it fixed?

risc0/risc0#634
https://docs.rs/getrandom/latest/getrandom/#opt-in-backends

The workaround as suggested by the above issue is to use a rust flag to tell getrandom a that custom backend will be used.

Opt-in backends can be enabled using the getrandom_backend configuration flag. The flag can be set either by specifying the rustflags field in [.cargo/config.toml](https://doc.rust-lang.org/cargo/reference/config.html):

# It's recommended to set the flag on a per-target basis:
[target.wasm32-unknown-unknown]
rustflags = ['--cfg', 'getrandom_backend="wasm_js"']

We can put in the config.toml so devs don't have to add it with environment variables.

To-Do

• I have read CONTRIBUTING.md.
• This PR title follows conventional commits.

[KolbyML]

I don't think this is a suitable solution

[syjn99]

Great! We might use .cargo/config.toml for applying this at all zkVM target compilation. This config.toml works for me:

[target.'cfg(target_os = "zkvm")']
rustflags = ["--cfg", "getrandom_backend=\"custom\""]

[KolbyML]

It looks like both of you guys didn't read this issue #857 @shariqnaiyer @syjn99

[KolbyML]

I will mark this PR as fixing the issue

[KolbyML]

@shariqnaiyer before we merge this, we should get the issues opened on hashsig/plonky3/ream first

[shariqnaiyer]

The following issues were made to handle this upstream:

Ream: #862
Hash-sig: b-wagn/hash-sig#90
Plonky3: Plonky3/Plonky3#1089

[KolbyML]

looks good