Missing fminf in compiler-builtins for soft-float

[todo]

See rust-lang/rust#62729.
As a workaround, we include the functions in libuser for now.

---

SunriseOS/libuser/src/terminal.rs

Lines 14 to 24 in 8b10070

	// TODO: Missing fminf in compiler-builtins for soft-float
	// BODY: See https://github.com/rust-lang/rust/issues/62729.
	// BODY:
	// BODY: As a workaround, we include the functions in libuser for now.
	/// Workaround rust-lang/rust#62729
	#[no_mangle]
	#[doc(hidden)]
	pub extern "C" fn fminf(x: f32, y: f32) -> f32 {
	libm::fminf(x, y)
	}

---

This issue was generated by todo based on a TODO comment in 8b10070 when #377 was merged. cc @roblabla.

[roblabla]

This got partially fixed by 0fd9a9e

However, it's still not fixed upstream. Instead we now use a fork of compiler-builtins that implements soft-float functions through a feature. This is suboptimal for a bunch of reasons (most importantly, the use of a feature instead of a target-feature makes this hard to upstream). Thus, I'm leaving this open.