perf(packaging): drop go build -a, keep JS deps between builds, no Metro in release mobile builds (untested on build machine)

[chrisnojima]

Not yet tested on a build machine. Hold this PR until test builds pass on macOS, iOS and Android.

What

Makes the release builds faster. Stacked on #29761.

• Go: drop -a. prerelease/build_keybase.sh, build_kbfs.sh, build_updater.sh and windows/build_prerelease.cmd no longer force a full rebuild, standard library included.
  • The build cache doesn't account for SDK headers in cgo code, so a new kb_guard_go_cache in lib.sh runs go clean -cache on macOS when the SDK version or build, the clang version, or MACOSX_DEPLOYMENT_TARGET changes.
• JS: stop clearing dependencies every build. The clearing was there because the build machines run low on disk.
  • Yarn cache: kb_prune_yarn_cache runs yarn cache clean only when the volume holding the cache has less than KB_MIN_FREE_GB free (default 30), and logs the free space either way.
  • node_modules: kb_yarn_modules keeps it and wipes it only when the stamp changes. The stamp covers yarn.lock, package.json, the patch names and contents, and the Node and yarn versions. It's deleted before each install, so a failed install is never reused.
  • Builds still run yarn modules, so postinstall, patch-package and the rnmodules sync still happen.
  • Android also deletes the native modules' node_modules/*/android/.cxx CMake caches.
• CLEAN_CACHES=1 forces a from-scratch build. When the bot sets it, kb_prune_yarn_cache always runs yarn cache clean, kb_yarn_modules always deletes node_modules, and kb_guard_go_cache always runs go clean -cache. The next build without the flag goes back to reusing the caches.
  • The macOS, Android and iOS entry scripts read it. keybot sets it when a build command gets --clean (keybot: --clean on build commands clears the build caches slackbot#118).
  • Windows isn't covered: build_prerelease.cmd doesn't use these helpers.
• Mobile: no Metro in release builds. The release variants bundle their own JS. manage_react_native_packager.sh is deleted, and nothing else in this repo or keybase/slackbot called it.
  • Android: shared/android/app/build.gradle:20-39 leaves debuggableVariants at its default of debug and debugOptimized, so release bundles. The script runs publishReleaseBundle.
  • iOS: the scheme's archive uses the Release configuration (Keybase.xcscheme:113-114). react-native-xcode.sh skips bundling only for Debug, and the bundle phase is at project.pbxproj:568-587.
  • Removed with it: shared/react-native/packageAndBuild.sh and the yarn rn:start:legacy script. Their only caller was the packager script, and the Jenkins Shellcheck stage and the README no longer list them.

Building the two macOS architectures in parallel (4.4 in the plan) is left out.

Tested locally

Stub tests with a fake yarn on PATH. The real cache wasn't touched.

Helper	Case	Result
kb_prune_yarn_cache	free space above the threshold	keeps the cache
	free space below the threshold	cleans it
	clean fails	non-fatal
kb_yarn_modules	first run	wipes and installs
	unchanged inputs	reuses node_modules
	lockfile, patch content or patch name changed	wipes
	install fails	returns non-zero, no stamp
	run after a failed install	wipes
CLEAN_CACHES=1	all three helpers, with warm caches	each one clears its cache
	the next run without it	reuses the caches again
kb_guard_go_cache (scratch GOCACHE)	first run	clears and stamps
	same toolchain	keeps the cache
	changed toolchain	clears

The test build must confirm

• macOS:
  • The log shows "…GB free (>= 30GB); keeping the yarn cache".
  • The second run logs "Dependencies unchanged; reusing node_modules", and the packaged app works.
  • The Go build is faster, and keybase version -S and kbfs -version are correct.
• iOS and Android:
  • The builds complete with no Metro running, and the installed TestFlight and Play internal builds launch with the embedded JS.
  • No expo start process is left behind.
• Patch change: after a change to shared/patches, the next build wipes node_modules and patch-package applies cleanly.
• Windows: build_prerelease.cmd builds without -a.

[Copilot]

🔵 Needs a closer look

The multi-platform release pipeline changes still require the stated macOS, iOS, Android, and Windows build-machine validation.

0 open findings

What changed in this PR

Optimizes multi-platform release packaging by reusing Go/JS caches and removing unnecessary Metro processes.

Changes:

• Reuses node_modules and conditionally prunes Yarn caches.
• Drops forced Go rebuilds while guarding macOS cache validity.
• Relies on native release bundling for Android and iOS.

File	Description
.github/​workflows/​shellcheck.yml	Removes deleted script from ShellCheck.
packaging/​README.md	Documents caching and mobile bundling.
packaging/​android/​build_and_publish.sh	Reuses dependencies and removes Metro startup.
packaging/​build_darwin.sh	Conditionally prunes the Yarn cache.
packaging/​desktop/​package_darwin.sh	Reuses unchanged JS dependencies.
packaging/​ios/​build_and_publish.sh	Reuses dependencies and removes Metro startup.
packaging/​lib.sh	Adds Yarn and Go cache helpers.
packaging/​manage_react_native_packager.sh	Deletes obsolete Metro management.
packaging/​prerelease/​build_app.sh	Guards the macOS Go cache.
packaging/​prerelease/​build_kbfs.sh	Removes forced Go rebuilds.
packaging/​prerelease/​build_keybase.sh	Removes forced Go rebuilds.
packaging/​prerelease/​build_updater.sh	Removes forced Go rebuilds.
packaging/​windows/​build_prerelease.cmd	Removes forced Windows Go rebuilds.
shared/​package.json	Removes the legacy Metro command.
shared/​react-native/​packageAndBuild.sh	Deletes the obsolete bundler launcher.

🧠 Review effort: Balanced

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