webpack_server: regenerate the package manifest PnP removed

[slarson-redo]

Problem

97e3e9b (Use Yarn PnP for nodejs_binary) dropped the CommonJS package manifest and the NODE_PACKAGE_MANIFEST export from nodejs/runner.sh.tpl. webpack/server/src/index.ts still reads that variable, so every webpack_server binary dies at startup:

Error: Unsupported path type: undefined
    at NodePathFS.mapToBase (…webpack.server_bin.pnp.cjs:10109:11)
    at NodePathFS.readFileSync (…webpack.server_bin.pnp.cjs:8665:42)
    at Object.<anonymous> (external/rules_javascript+/webpack/server/src/index.js:17:61)

(fs.readFileSync(undefined, "utf8"), via PnP's patched fs.)

Why the manifest is not vestigial

PnP resolves the dev server's own requires, so the obvious fix — deleting the manifest read — looked right. It isn't. The dev server bundles files out of the tool tree, and webpack resolves their imports from the filesystem, where PnP materializes nothing. Removing the fs-linker view instead produces:

ERROR in …/redo_npm_webpack_5.94.0/files/hot/emitter.js
Module not found: Error: Can't resolve 'events'
ERROR in …/redo_npm_pmmmwh_react-refresh-webpack-plugin_0.5.17/files/client/ReactRefreshEntry.js
Module not found: Error: Can't resolve 'core-js-pure/features/global-this'

and, before that, webpack-dev-server's isInstalled node_modules walk fails, so it prompts to yarn add -D webpack-cli. (webpack/runtime only fakes process.versions.pnp for webpack's own checkPackageExists, not for the dev server's isInstalled.)

Fix

webpack_server generates the manifest itself instead of borrowing nodejs_binary's.

It needs the server binary's CommonJS graph in the binary's own configuration — a plain cfg = "exec" attribute would not match, because nodejs_binary's dep goes through nodejs_transition (//javascript:module = "node"), and mismatched paths would make the manifest point at files that are not in runfiles. So nodejs_binary forwards its dep's CjsInfo, WebpackInfo carries it as server_cjs, and _webpack_server_impl runs gen_manifest over it with to_rlocation_path package paths — the same shape nodejs_binary used to emit. webpack/server-runner.sh.tpl exports NODE_PACKAGE_MANIFEST from it; the shim is unchanged.

Verification

Against redo at the 4b6fe19 pin, carrying this as an archive_override patch:

• bazel run //redo/shopify/extension:server — starts, webpack 5.94.0 compiled successfully, no unresolved modules, serves main.js with HTTP 200 / 6,132,734 bytes.
• Every webpack_server, webpack_bundle, and nodejs_binary target in redo builds.

Before the fix, the same target crashed on NODE_PACKAGE_MANIFEST at startup.