test-float-parse: apply cfg(not(bootstrap))

Prior to stage 0 redesign, `test-float-parse` ran against in-tree std
but now it runs against beta std. `f16::FromStr` were only present in
in-tree std and not yet beta std, so apply `cfg(not(bootstrap))` gating
to unbrick `./x check --stage=0`.

Author: jieyouxu

src/etc/test-float-parse/src/lib.rs

@@ -119,6 +119,7 @@ pub fn register_tests(cfg: &Config) -> Vec<TestInfo> {
 
     // Register normal generators for all floats.
 
+    #[cfg(not(bootstrap))]
     #[cfg(target_has_reliable_f16)]
     register_float::<f16>(&mut tests, cfg);
     register_float::<f32>(&mut tests, cfg);

src/etc/test-float-parse/src/traits.rs

@@ -170,6 +170,7 @@ macro_rules! impl_float {
 
 impl_float!(f32, u32; f64, u64);
 
+#[cfg(not(bootstrap))]
 #[cfg(target_has_reliable_f16)]
 impl_float!(f16, u16);