Allow the ability to specifiy build output file extension via project.json

[Ked29]

A small feature request is the ability to specify a build output file extension in project.json, as shown below. This helps developers who need a different file extension for specific use cases/scenarios and allows them to not have to manually rename the build output to that extension every time.

{
  "langrev": "1",
  "warnings": [ "no-unused" ],
  "dependency-search-paths": [ "lib" ],
  "dependencies": [ ],
  "linker-search-paths": ["lib"],
  "linked-libraries": [ ],
  "authors": [ "Me" ],
  "version": "0.1.0",
  "sources": [ "src/**" ],
  "output": "build",
  "targets": {
    "MyProject": {
      "type": "dynamic-lib",
      "extension": ".asi"
    }
  },
  "cpu": "generic",
  "opt": "O0",
}

[Josecespedesant]

Hello! Can I take a look at this issue?

[lerno]

Yes, absolutely.

[Josecespedesant]

Thank you! Will work on this