Signed-off-by: Joe Richey <joerichey@google.com>

Cloud ABI [is now Tier 3](https://github.com/rust-lang/rust/pull/75568),
so its libstd is no longer distributed with Rust.

Firefox testing is also disabled due to:
  https://github.com/rustwasm/wasm-bindgen/issues/2261



Signed-off-by: Joe Richey <joerichey@google.com>

Also, pin the version of rustc, so that nightly updates don't break
our build. This means that we can add the nightlies back into the
blocking set of tests.

Update the Ubuntu version to 20.04
Don't run any cargo-web tests (upstream is broken)

Signed-off-by: Joe Richey <joerichey@google.com>

Split emscripten stuff into its own target and stop relying on cargo web
to download/manage then emscripten toolchain. We can just get it
ourselves. We also now run the emscripten tests.

Signed-off-by: Joe Richey <joerichey@google.com>

We no longer use spin-locks anywhere in getrandom, so remove any
interfaces which spin.

Signed-off-by: Joe Richey <joerichey@google.com>

Don't spin when polling /dev/random. We also remove the use of spin
locks when opening the persistent fd for platforms that require it.

For both these cases, we can just use the pthread lock/unlock methods
in libc. This includes adding Mutex and DropGuard abstractions.

Signed-off-by: Joe Richey <joerichey@google.com>

Signed-off-by: Joe Richey <joerichey@google.com>

Rename it from freebsd.rs to sysctl_arandom.rs.

NetBSD has been patching rustc for some time to use the FreeBSD
implementation because every single invocation of the compiler
may drain from the entropy pool and cause the next to block.

This can massively inflate build times for rust software, or cause
it to fail entirely, especially in VMs (for example, our Xen package
building cluster).

cfg-if 0.1.2 is minimal version of dependency

Fix and Improve WASM CI

- Use latest Firefox
- Explicitly pin wasmtime and cargo-web
- Make sure our `wasm-bindgen-test-runner` and `wasm-bindgen` versions match

Run Rustfmt

* Simplify CI process for WASM

Run WASI tests, and run both stdweb/wasm-bindgen on both node and in browsers

These changes also remove the need for a separate tests/wasm_bindgen

* Use all pre-built binaries in the CI

* Fix Cargo.toml typo

Co-Authored-By: Artyom Pavlov <newpavlov@gmail.com>

* Fix install location

* Debug CI

Ensure and document that we do nothing when an empty slice is passed.

Note that this changes are for consistency, not to prevent UB.

* Fix Redox CI

* Bump libc version to fix Redox

This updates the documentation to explain exactly what we are doing on
this target. Also adds a test that the target builds without features.