`tracing-core` does not compile on `thumbv6m-none-eabi` with `--no-default-features`

[Pratyush]

Bug Report

tracing-core does not compile on thumbv6m-none-eabi.

Version

tracing-core: 0.1.16

Platform

Linux, but cross-compiling to thumbv6m-non-eabi

Affected Crates

tracing-core, and hence all downstream tracing crates

Bug

Running cargo check --no-default-features --target thumbv6m-none-eabi in tracing-core fails.

It seems that compare-and-swap (and alloc::sync) are not enabled on this target: rust-lang/rust#51953