Add some posix_spawn apple extension flags

Revert "Link to libgcc when statically linking musl"

This causes linker errors due to duplicated symbols. See https://github.com/rust-lang/rust/pull/52157

This reverts commit 920cfeac.

Add MODULE_INIT_ constants

These are flags required to implement the linux kernel loading mechanism.
Specifically finit_module.

These are flags required to implement the linux kernel loading mechanism.
Specifically finit_module.

Implement statfs for dragonfly, freebsd and openbsd

Openbsd fix

put in several fixes for OpenBSD (one fix per commit).
testsuite ran on OpenBSD 6.3-current (upcoming 6.4)

```
RUNNING ALL TESTS
PASSED 6474 tests
```

they doesn't exists on OpenBSD. put them under NetBSD specific tree.

Fix netbsd build with "stdbuild"

A bug was introduced in #930 which caused netbsd to not link to libm.

r? @alexcrichton

Fix a #[cfg] attribute

It looks like this was a mistake of #930 but should be easy to fix!

It looks like this was a mistake of #930 but should be easy to fix!

Link to libgcc when statically linking musl

On some architectures (e.g. aarch64) musl depends on some libgcc functions (`__addtf3`, `__multf3`, `__subtf3`) for `long double` arithmetic that it uses internally. Unfortunately we don't provide these functions in compiler-builtins, so we instead need to get them from libgcc.

Fixes:
https://github.com/rust-lang/rust/issues/46651
https://github.com/rust-lang-nursery/compiler-builtins/issues/201
https://github.com/rust-lang-nursery/compiler-builtins/issues/217

Bump ctest from `482c7f0` to `5c53723`

Bumps [ctest](https://github.com/alexcrichton/ctest) from `482c7f0` to `5c53723`.
<details>
<summary>Commits</summary>

- [`5c53723`](https://github.com/alexcrichton/ctest/commit/5c537236d150da311d67b8ccf4c3c49987b92c8d) Update libc dep
- See full diff in [compare view](https://github.com/alexcrichton/ctest/compare/482c7f0643942174a802d89ad7d460e89b576ed3...5c537236d150da311d67b8ccf4c3c49987b92c8d)
</details>
<br />

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`.

---

**Note:** This repo was added to Dependabot recently, so you'll receive a maximum of 5 PRs for your first few update runs. Once an update run creates fewer than 5 PRs we'll remove that limit.

You can always request more updates by clicking `Bump now` in your [Dependabot dashboard](https://app.dependabot.com).

<details>
<summary>Dependabot commands and options</summary>
<br />

You can trigger Dependabot actions by commenting on this PR:
- `@dependabot rebase` will rebase this PR
- `@dependabot merge` will merge this PR after your CI passes on it
- `@dependabot ignore this [patch|minor|major] version` will close this PR and stop Dependabot creating any more for this minor/major version (unless you reopen the PR or upgrade to it yourself)
- `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
- `@dependabot use these labels` will set the current labels as the default for future PRs for this repo and language
- `@dependabot use these reviewers` will set the current reviewers as the default for future PRs for this repo and language
- `@dependabot use these assignees` will set the current assignees as the default for future PRs for this repo and language
- `@dependabot badge me` will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot [dashboard](https://app.dependabot.com):
- Update frequency (including time of day and day of week)
- Automerge options (never/patch/minor, and dev/runtime dependencies)
- Pull request limits (per update run and/or open at any time)
- Out-of-range updates (receive only lockfile updates, if desired)
- Security updates (receive only security updates, if desired)

Finally, you can contact us by mentioning @dependabot.

</details>

Bumps [ctest](https://github.com/alexcrichton/ctest) from `482c7f0` to `5c53723`.
- [Release notes](https://github.com/alexcrichton/ctest/releases)
- [Commits](https://github.com/alexcrichton/ctest/compare/482c7f0643942174a802d89ad7d460e89b576ed3...5c537236d150da311d67b8ccf4c3c49987b92c8d

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Add if_packet.h headers

Some structs for implementing af_packet(7)

Some structs for implementing af_packet(7)

Add linux musl powerpc (32-bit) support

This change adds support for musl on 32-bit powerpc.  Most of the general constants in src/unix/notbsd/linux/musl/b32/mod.rs were different from those of the powerpc port, so I moved them over to the individual architecture-specific submodules.  The same with the ipc_perm structure.

Add ENOATTR for Android

PR based on https://github.com/rust-lang/libc/pull/594

It's defined in Android sysroot so it should work without test workaround (CI should catch it otherwise?).