saw-rustc doesn't work with const or static values

[RyanGlScott]

pub static X: u32 = 0;
pub const Y: u32 = 0;

pub fn z() -> u32 {
    X + Y
}

$ saw-rustc wat.rs
test build - extract output path - ["rustc", "wat.rs", "--test", "--target", "x86_64-unknown-linux-gnu", "--cfg", "crux"]
test build - ["rustc", "wat.rs", "--target", "x86_64-unknown-linux-gnu", "--cfg", "crux", "--cfg", "crux_top_level", "--crate-type", "rlib"]
note: Emitting MIR for wat/7d4d1b88::X

error: #[test] can only be applied to functions
 --> wat.rs:1:1
  |
1 | pub static X: u32 = 0;
  | ^^^^^^^^^^^^^^^^^

error: #[test] can only be applied to functions
 --> wat.rs:2:1
  |
2 | pub const Y: u32 = 0;
  | ^^^^^^^^^^^^^^^^

note: Emitting MIR for wat/7d4d1b88::z

error: aborting due to 2 previous errors

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ErrorGuaranteed(())', src/bin/mir-json-rustc-wrapper.rs:252:65
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Given that this is the third issue of this sort that we've opened (after #53 and #47), I wonder if we should rethink our approach to what saw-rustc disallows.

[spernsteiner]

The "#[test] can only be applied to functions" error doesn't really make sense for saw-rustc, where the #[crux::test] attribute is not actually used. Maybe saw-rustc should silently skip unsupported definitions where crux-rustc would produce this error. Then the saw-rustc output would include every function where you could have legally applied #[crux::test].