Re-enable testing of WASI on CI

This commit updates CI to resume testing WASI. This updates the
container and testing scripts from historical processes to more modern
ones, e.g. downloading wasi-sdk instead of compiling a custom toolchain.
This should make it easier to update in the future and keep it in sync
with rust-lang/rust as well.

This also required a few minor fixes such as:

* The `S_IFIFO` and `S_IFMT` constants had incorrect values.
* The `CLOCK_*` definitions cause `ctest2`'s parsing to panic to they're
  skipped with a new `#[cfg]`.
* A new `langinfo.h` header was added to the list to include.
* Some historically skipped checks were removed since they're no longer
  necessary.
* Checks for `__errno_location` are disabled since that doesn't actually
  exist in headers.
* Checks for `select` are disabled because the Rust definition got the
  `const`-ness swapped for the final `timeval` argument.

(backport <rust-lang#3869>)
[ resolve conflicts - Trevor ]
(cherry picked from commit 7c10562)

Author: alexcrichton

Diff for: .github/workflows/full_ci.yml

@@ -118,11 +118,7 @@ jobs:
           powerpc64le-unknown-linux-gnu,
           s390x-unknown-linux-gnu,
           riscv64gc-unknown-linux-gnu,
-          # FIXME: A recent nightly causes a linker failure:
-          # https://github.com/rust-lang/rust/issues/76679
-          # See this comment for more details:
-          # https://github.com/rust-lang/libc/pull/2225#issuecomment-880696737
-          #wasm32-wasi,
+          wasm32-wasip1,
           sparc64-unknown-linux-gnu,
           wasm32-unknown-emscripten,
           x86_64-linux-android,