"First class" targets

[Idorobots]

Would be nice for the compilation targets to determine the compilation pipeline - for instance:

• omitting certain phases on a target that doesn't need them,
• including extra/fewer built-in modules if a runtime provides it.

Each target should provide a compiler built out of the current pipeline parts as well as a command to execute the code and run a REPL.

Compiler options:

• --target - sets the compilation target, which sets the default compiler options and then applies overrides from the command line (for instance js),
• --platform - sets the target-specific platform (e.g. nodejs),
• --runtime - sets the target-specific runtime (if there are multiple provided),
• --packaging - target specific packaging (for example, module vs standalone).

sprtn run -i test.sprtn --target ES6 --platform nodejs --packaging module

Alternatively, the options can be combined into a single target string:

sprtn run -i test.sprtn --target es6-nodejs-module
sprtn run -i test.sprtn --target native-x86_64-shared