3 If you'd like to build for a target that is not yet supported by `rustc`, you can use a
4 "custom target specification" to define a target. These target specification files
5 are JSON. To see the JSON for the host target, you can run:
8 $ rustc +nightly -Z unstable-options --print target-spec-json
11 To see it for a different target, add the `--target` flag:
14 $ rustc +nightly -Z unstable-options --target=wasm32-unknown-unknown --print target-spec-json
17 To use a custom target, see the (unstable) [`build-std` feature](https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-std) of `cargo`.