Alternate PR for clojurescript: clojurescript-compiler

@adamv

The arguments in #21733 favor the removal of the clojure formula, and I'm in agreement with those. The clojure formula is superfluous: `leiningen` is all you need to get started with clojure. However, those arguments do not carry over to the case of `clojurescript`.

`clojurescript` is a compiler that can be run independently from `leiningen`. It compiles clojure source files down to javascript.

The clojurescript devs refer new users to `leiningen`, but also include instructions on how to install `clojurescript` separately. This is useful anytime you want to invoke the compiler outside of a project, in editor extensions, custom tooling, etc. Currently, it is not possible to use `leiningen` as a single-shot build tool against arbitrary files.

Those instructions are documented in the quick start section of the wiki.

https://github.com/clojure/clojurescript/wiki/Quick-Start

In the resulting installation, `clojurescript` can be run independently. This formula proposes to automate those prescriptions.

In addition to caveats, I propose to rename the recipe to `clojurescript-compiler` so as to not to lure beginners. This is a formula similar in spirit as the `closure-compiler` formula.