Change to `Ord::clamp` causes build errors by calling through upstream monomorphisations

[Dan54]

Following rust-lang/rust#147754, chromium encounters the following build error:

error: `compiler_builtins` cannot call functions through upstream monomorphizations; encountered invalid call from `core::fmt::num::<impl core::fmt::Debug for i32>::fmt` to `core::fmt::num::imp::<impl core::fmt::Display for i32>::fmt`
 --> ./../../third_party/rust-toolchain/lib/rustlib/src/rust/library/core/src/fmt/num.rs:79:0
 ::: ./../../third_party/rust-toolchain/lib/rustlib/src/rust/library/core/src/fmt/num.rs:97:1
  |
  = note: in this expansion of `impl_Debug!`
 ::: ./../../third_party/rust-toolchain/lib/rustlib/src/rust/library/core/src/fmt/num.rs:592:1
  |
  = note: in this macro invocation

The clamp() function is called twice in libm/src/math/genric/scalbn.rs (at lines 99 and 106). I think the easiest fix would be to replace these calls with a locally defined clamp() that doesn't call Debug::fmt.