add host feature to jolt-core

[flyq]

When I comiple the jolt-core to wasm:

   Compiling jolt-core v0.1.0 (https://github.com/a16z/jolt#6083da83)
error[E0432]: unresolved import `tokio::runtime::Runtime`
  --> /Users/flyq/.cargo/git/checkouts/jolt-6b856340b98daf0c/6083da8/jolt-core/src/host/toolchain.rs:12:5
   |
12 | use tokio::runtime::Runtime;
   |     ^^^^^^^^^^^^^^^^^^^^^^^ no `Runtime` in `runtime`

error[E0433]: failed to resolve: could not find `time` in `tokio`
   --> /Users/flyq/.cargo/git/checkouts/jolt-6b856340b98daf0c/6083da8/jolt-core/src/host/toolchain.rs:49:24
    |
49  |                 tokio::time::sleep(std::time::Duration::from_millis(timeout)).await;
    |                        ^^^^ could not find `time` in `tokio`
    |
note: found an item that was configured out
   --> /Users/flyq/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.37.0/src/lib.rs:549:13
    |
549 |     pub mod time;
    |             ^^^^
    = note: the item is gated behind the `time` feature

error[E0603]: module `runtime` is private
   --> /Users/flyq/.cargo/git/checkouts/jolt-6b856340b98daf0c/6083da8/jolt-core/src/host/toolchain.rs:12:12
    |
12  | use tokio::runtime::Runtime;
    |            ^^^^^^^ private module
    |
note: the module `runtime` is defined here
   --> /Users/flyq/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.37.0/src/lib.rs:522:5
    |
522 |     pub(crate) mod runtime;
    |     ^^^^^^^^^^^^^^^^^^^^^^

error[E0599]: no method named `chunk` found for struct `Response` in the current scope
   --> /Users/flyq/.cargo/git/checkouts/jolt-6b856340b98daf0c/6083da8/jolt-core/src/host/toolchain.rs:120:42
    |
120 |         while let Some(chunk) = response.chunk().await.unwrap() {
    |                                          ^^^^^ method not found in `Response`

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
   --> /Users/flyq/.cargo/git/checkouts/jolt-6b856340b98daf0c/6083da8/jolt-core/src/host/toolchain.rs:120:19
    |
120 |         while let Some(chunk) = response.chunk().await.unwrap() {
    |                   ^^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `[u8]`
note: required by a bound in `std::prelude::v1::Some`
   --> /Users/flyq/.rustup/toolchains/nightly-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/option.rs:571:17
    |
571 | pub enum Option<T> {
    |                 ^ required by this bound in `std::prelde::v1::Some`
...
579 |     Some(#[stable(feature = "rust1", since = "1.0.0")] T),
    |     ---- required by a bound in this tuple variant

Some errors have detailed explanations: E0277, E0432, E0433, E0599, E0603.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `jolt-core` (lib) due to 5 previous errors

tokio and reqwest are not friendly to wasm, and only the host mod depends on them. So I added host features to achieve conditional compilation

[flyq]

https://github.com/a16z/jolt/issues/314

[ncitron]

What are you trying to do with wasm specifically? Wouldn't you need access to the host code if your trying to generate proofs in wasm?

[flyq]

What are you trying to do with wasm specifically?

My current goal is to compile jolt's verify function into wasm(on chain). verify depends on jolt-core. Tokio and reqwest in jolt-core prevent verify from being compiled into wasm.

Wouldn't you need access to the host code if your trying to generate proofs in wasm?

I generate the proof locally, and only verify the proof in wasm. Yes, I don't need host-related code, so my dependencies are set up like this to avoid introducing host-related logic:

jolt-core = { git = "https://github.com/zkp-learning/jolt", default-features = false, features = [
    "multicore",
] }