Make setup-wasm script work for local dev

[padmaia]

This updates scripts/setup-wasm.mjs to work locally when it previously only worked for GH Actions. Also added some explanation for building the wasm binary in contributing.md.

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
buildDuration	19.9s	20.5s	⚠️ +580ms
buildDurationCached	8s	7.6s	-412ms
nodeModulesSize	481 MB	481 MB	✓

Page Load Tests Overall increase ✓

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
/ failed reqs	0	0	✓
/ total time (seconds)	4.362	4.237	-0.12
/ avg req/sec	573.15	590.01	+16.86
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.142	2.045	-0.1
/error-in-render avg req/sec	1167.3	1222.66	+55.36

Client Bundles (main, webpack)

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
925.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	28.5 kB	28.5 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	72.1 kB	72.1 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	192 B	192 B	✓
amp-HASH.js gzip	309 B	309 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	3.04 kB	3.04 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	920 B	920 B	✓
image-HASH.js gzip	5.74 kB	5.74 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.36 kB	2.36 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	392 B	392 B	✓
withRouter-HASH.js gzip	319 B	319 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16 kB	16 kB	✓

Client Build Manifests

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
_buildManifest.js gzip	461 B	461 B	✓
Overall change	461 B	461 B	✓

Rendered Page Sizes

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
index.html gzip	532 B	532 B	✓
link.html gzip	545 B	545 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
buildDuration	22.5s	22.6s	⚠️ +82ms
buildDurationCached	7.4s	7.6s	⚠️ +194ms
nodeModulesSize	481 MB	481 MB	✓

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
/ failed reqs	0	0	✓
/ total time (seconds)	4.402	4.361	-0.04
/ avg req/sec	567.95	573.33	+5.38
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	2.132	2.207	⚠️ +0.07
/error-in-render avg req/sec	1172.63	1132.82	⚠️ -39.81

Client Bundles (main, webpack)

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
925.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.9 kB	28.9 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.8 kB	72.8 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	179 B	179 B	✓
amp-HASH.js gzip	313 B	313 B	✓
css-HASH.js gzip	325 B	325 B	✓
dynamic-HASH.js gzip	3.02 kB	3.02 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	921 B	921 B	✓
image-HASH.js gzip	5.79 kB	5.79 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	2.44 kB	2.44 kB	✓
routerDirect..HASH.js gzip	322 B	322 B	✓
script-HASH.js gzip	393 B	393 B	✓
withRouter-HASH.js gzip	317 B	317 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16.1 kB	16.1 kB	✓

Client Build Manifests

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
_buildManifest.js gzip	457 B	457 B	✓
Overall change	457 B	457 B	✓

Rendered Page Sizes

	vercel/next.js canary	padmaia/next.js chore/setup-wasm-local	Change
index.html gzip	532 B	532 B	✓
link.html gzip	546 B	546 B	✓
withRouter.html gzip	527 B	527 B	✓
Overall change	1.6 kB	1.6 kB	✓

Commit: c6a82f1

[ijjk]

Failing test suites

Commit: c6a82f1

yarn testheadless test/integration/cli/test/index.test.js

• CLI Usage > info > should print output

Expand output

● CLI Usage › info › should print output

expect(received).toBe(expected) // Object.is equality

Expected: ""
Received: "warn  - Failed to fetch latest canary version. Visit https://github.com/vercel/next.js/releases. Detected \"12.1.6-canary.5\".
      Make sure to try the latest canary version (`npm install next@canary`) to confirm the issue still exists before creating a new issue.
      Read more - https://nextjs.org/docs/messages/opening-an-issue
"

  496 |       // warning will show so skip this check for the stable release
  497 |       if (pkg.version.includes('-canary')) {
> 498 |         expect(info.stderr || '').toBe('')
      |                                   ^
  499 |       }
  500 |       expect(info.stdout).toMatch(
  501 |         new RegExp(`

  at Object.<anonymous> (integration/cli/test/index.test.js:498:35)

Read more about building and testing Next.js in contributing.md.