These changes bring the types up to parity with recent Emscripten
versions using the upstream LLVM wasm backend. These changes should be
coordinated with the upgrade of rustc's Emscripten support. See
https://internals.rust-lang.org/t/upgrading-rust-s-emscripten-support/10684

libc currently denies all warnings by default. This commit denies
warnings only when libc is built in CI.

Define the C interface to vxWorks for x86, x86_64, ARM, ARM 64-bit, PowerPC, PowerPC SPE and PowerPC 64-bit.

Currently, libc supports and detects freebsd11 and freebsd13
Unknown versions, like freebsd13, is treated as freebsd11.
This patch solve the issues, detecting freebsd13 and treating it like
freebsd12.
Inverting the logic not(freebsd12) -> freebsd11 where possible

Currently, libc supports and detects freebsd11 and freebsd13
Unknown versions, like freebsd13, is treated as freebsd11.
This patch solve the issues, detecting freebsd13 and treating it like
freebsd12.
Inverting the logic not(freebsd12) -> freebsd11 where possible

Signed-off-by: Diana Popa <dpopa@amazon.com>

Exposes value for most unix like platforms

These constants have already been deprecated for a few releases with
a deprecation notice, so they can finally be removed.

Closes rust-lang/libc#665

Per discussion in #1410, this is necessary to avoid struct size mismatches between Rust and C on
systems with glibc < 2.28.

Add cfg_attr