Add NEXT_MANUAL_SIG_HANDLE handling to start-server.ts

[mdio]

If a manual signal handler is registered, SIGINT and SIGTERM should not be handled by Next.js. This was already the case in the standalone server.js but was missing here, rendering the env flag useless.

With this fix, the example given in https://nextjs.org/docs/pages/building-your-application/deploying#manual-graceful-shutdowns is working (again).

Fixes #56810.

[ijjk]

Stats from current PR

Default Build

General Overall increase ⚠️

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
buildDuration	10.7s	10.4s	N/A
buildDurationCached	5.9s	6s	⚠️ +120ms
nodeModulesSize	199 MB	199 MB	⚠️ +676 B
nextStartRea..uration (ms)	423ms	420ms	N/A

Client Bundles (main, webpack)

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
199-HASH.js gzip	30.7 kB	30.7 kB	N/A
3f784ff6-HASH.js gzip	53.3 kB	53.3 kB	✓
494.HASH.js gzip	180 B	181 B	N/A
framework-HASH.js gzip	45.2 kB	45.2 kB	✓
main-app-HASH.js gzip	241 B	238 B	N/A
main-HASH.js gzip	31.7 kB	31.7 kB	N/A
webpack-HASH.js gzip	1.7 kB	1.7 kB	✓
Overall change	100 kB	100 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
_app-HASH.js gzip	194 B	195 B	N/A
_error-HASH.js gzip	182 B	181 B	N/A
amp-HASH.js gzip	501 B	503 B	N/A
css-HASH.js gzip	322 B	323 B	N/A
dynamic-HASH.js gzip	2.5 kB	2.5 kB	✓
edge-ssr-HASH.js gzip	253 B	255 B	N/A
head-HASH.js gzip	348 B	347 B	N/A
hooks-HASH.js gzip	369 B	368 B	N/A
image-HASH.js gzip	4.27 kB	4.27 kB	N/A
index-HASH.js gzip	256 B	256 B	✓
link-HASH.js gzip	2.61 kB	2.6 kB	N/A
routerDirect..HASH.js gzip	311 B	311 B	✓
script-HASH.js gzip	384 B	383 B	N/A
withRouter-HASH.js gzip	307 B	308 B	N/A
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Overall change	3.17 kB	3.17 kB	✓

Client Build Manifests

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
_buildManifest.js gzip	484 B	483 B	N/A
Overall change	0 B	0 B	✓

Rendered Page Sizes

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
index.html gzip	529 B	527 B	N/A
link.html gzip	541 B	542 B	N/A
withRouter.html gzip	525 B	522 B	N/A
Overall change	0 B	0 B	✓

Edge SSR bundle Size

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
edge-ssr.js gzip	92.6 kB	92.6 kB	N/A
page.js gzip	145 kB	145 kB	N/A
Overall change	0 B	0 B	✓

Middleware size

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
middleware-b..fest.js gzip	624 B	624 B	✓
middleware-r..fest.js gzip	150 B	151 B	N/A
middleware.js gzip	35.7 kB	35.7 kB	✓
edge-runtime..pack.js gzip	1.92 kB	1.92 kB	✓
Overall change	38.3 kB	38.3 kB	✓

Next Runtimes

	vercel/next.js canary	mdio/next.js fix-manual-sig-handle	Change
app-page-exp...dev.js gzip	168 kB	168 kB	✓
app-page-exp..prod.js gzip	93.7 kB	93.7 kB	✓
app-page-tur..prod.js gzip	94.5 kB	94.5 kB	✓
app-page-tur..prod.js gzip	89 kB	89 kB	✓
app-page.run...dev.js gzip	138 kB	138 kB	✓
app-page.run..prod.js gzip	88.4 kB	88.4 kB	✓
app-route-ex...dev.js gzip	24.2 kB	24.2 kB	✓
app-route-ex..prod.js gzip	16.8 kB	16.8 kB	✓
app-route-tu..prod.js gzip	16.9 kB	16.9 kB	✓
app-route-tu..prod.js gzip	16.4 kB	16.4 kB	✓
app-route.ru...dev.js gzip	23.6 kB	23.6 kB	✓
app-route.ru..prod.js gzip	16.4 kB	16.4 kB	✓
pages-api-tu..prod.js gzip	9.37 kB	9.37 kB	✓
pages-api.ru...dev.js gzip	9.64 kB	9.64 kB	✓
pages-api.ru..prod.js gzip	9.37 kB	9.37 kB	✓
pages-turbo...prod.js gzip	21.9 kB	21.9 kB	✓
pages.runtim...dev.js gzip	22.6 kB	22.6 kB	✓
pages.runtim..prod.js gzip	21.9 kB	21.9 kB	✓
server.runti..prod.js gzip	49.3 kB	49.3 kB	✓
Overall change	930 kB	930 kB	✓

Commit: b738217

[ztanner]

Thanks!