This change allows `crate_universe` to use a custom repo for the rust toolchain. I.e. suppose that `cargo` and `rustc` come from a custom repo rule and have different paths inside the repo rule (compared to the standard "upstream")
Fixes #1019
* Add support for WebAssembly.
* Add a comment explaining that the npm deps are for the wasm example.
* Use transitions for web assembly.
* Upgrade WASM bindgen and make compatible with Typescript.
* Remove unnecessary setting.
* Re-run cargo-raze.
* Add nodejs rules for the examples workspace.
* Fix link_env missing.
* Bazel 1.0 compatibility.
* Exclude matrix_dylib_test on RBE due to https://github.com/bazelbuild/bazel/issues/9987.
* Ignore the wasm test because rust-lld isn't available on RBE.
* Use extra target triples.
* Remove extra newline.
Ivan Kalchev