Allow makefile addition to build Go wasip1 .wasm binary

[WietseWind]

With Go supporting wasi (wasip1 os) now (as mentioned here: https://go.dev/blog/wasi & here #3300), this PR adds a build option to the Makefile for a wasip1 wasm build.

Tested & runs prefectly fine with wasmtime:

wasmtime --dir=.::/ /npm/@esbuild/wasip1-wasm/bin/esbuild.wasm --help

^^ Heads up! In case of wasmtime, the dir arg needs exactly this content: .::/ - which means . (local dir) maps to (::) / (root virtual filesystem).

The advantage of building wasi over the current wasm build (platform-wasm) is that the wasi build can run natively using CLI tools like wasmtime, and running in a node / JS environment is also compatible with several wasi browser runtimes. So: no need for the specific esbuild-wasm package, as one can execute the built .wasm with e.g. @runno/wasi or any other wasi implementation.

To run the same thing not on CLI but in a browser, all you need is this in a <script type="module" ...:

import { WASI } from "@runno/wasi"

const esbuild_wasip1 = 'https://qkbtifg.dlvr.cloud/esbuild.wasm' // needs nginx mime type application/wasm wasm;

const result = WASI.start(fetch(esbuild_wasip1), {
  // env: { SOME_KEY: "some value" },
  args: ['esbuild', 'file.ts', '--bundle', '--minify', '--platform=browser', '--format=esm', '--target=es2017'],
  stdout: out => document.write(`<pre>${out}</pre>`),
  stderr: err => console.log("stderr:" + err),
  stdin: () => undefined,
  fs: {
    "/file.ts": {
      path: "/file.ts",
      timestamps: { access: new Date(), change: new Date(), modification: new Date(), },
      mode: "string",
      content: (`
        // Some TS content...
        const v: string = 'Trololo works like a charm!'
        console.log(v)
      `),
    },
  },
})