Fails to compile in Alpine Linux Docker container.

Describe the bug you encountered:

Pyroscope failed to compile in docker container running Alpine Linux, with error:

   Compiling pyroscope v0.5.3
error[E0277]: the trait bound `*mut c_void: Default` is not satisfied
  --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/pyroscope-0.5.3/src/utils.rs:78:31
   |
78 |     let thread_id = check_err(unsafe { libc::pthread_self() })? as u64;
   |                     --------- ^^^^^^^^^--------------------^^
   |                     |         |        |
   |                     |         |        this tail expression is of type `*mut libc::c_void`
   |                     |         the trait `Default` is not implemented for `*mut c_void`
   |                     required by a bound introduced by this call
   |
note: required by a bound in `check_err`
  --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/pyroscope-0.5.3/src/utils.rs:54:27
   |
54 | pub fn check_err<T: Ord + Default>(num: T) -> Result<T> {
   |                           ^^^^^^^ required by this bound in `check_err`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `pyroscope` due to previous error
warning: build failed, waiting for other jobs to finish...
thread 'main' panicked at 'Exited with status code: 101', /root/.cargo/registry/src/github.com-1ecc6299db9ec823/cargo-chef-0.1.44/src/recipe.rs:161:27
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
The command '/bin/sh -c cargo chef cook --release --target x86_64-unknown-linux-musl --recipe-path recipe.json' returned a non-zero code: 101

What did you expect to happen instead?

Pyroscope should compile.

How did you install pyroscope-rs?

In Cargo.toml:

[dependencies]
pyroscope = "0.5.3"
pyroscope_pprofrs = "0.2"

pyroscope-rs version and environment

pyroscope-rs 0.5.3 on Alpine (Musl libC).

I am able to compile it with native toolchains on my Ubuntu machine, so I suspect this is due to alpine using Musl libc instead of glibc (especialy considering the error relates to libc bindings).

I attached an archive of a minimal example demonstrating the issue. It's just the "basic" pyroscope example separated out as its own project, along with a Dockerfile and .dockerignore.

pyroscope_alpine_bug.zip

grafana / pyroscope-rs

Fails to compile in Alpine Linux Docker container. #64