target_feature attribute should only be applied to `unsafe` functions

[lucasly-ba]

code:

#[target_feature]
fn foo_sse() {}

expected output:

error: malformed `target_feature` attribute input
 --> a.rs:2:1
  |
2 | #[target_feature]
  | ^^^^^^^^^^^^^^^^^ help: must be of the form: `#[target_feature(enable = "name")]`

error[E0658]: `#[target_feature(..)]` can only be applied to `unsafe` functions
 --> a.rs:2:1
  |
2 | #[target_feature]
  | ^^^^^^^^^^^^^^^^^
3 | fn foo_sse() {}
  | ------------ not an `unsafe` function
  |
  = note: see issue #69098 <https://github.com/rust-lang/rust/issues/69098> for more information

error: aborting due to 2 previous errors