[macOS] Eliminate archive_gen_snapshot target

[cbracken]

This target produced an unused zipfile named gen_snapshot.zip containing the gen_snapshot_${target_arch} binary for the current build's target architecture.

The macOS recipe JSON produces the real gen_snapshot.zip that gets uploaded to the cloud bucket and pulled down by the tool. See:

engine/ci/builders/mac_host_engine.json

Lines 555 to 592 in e5215e6

	{
	"name": "Debug-gen_snapshots",
	"parameters": [
	"--dst",
	"out/debug/snapshot",
	"--arm64-out-dir",
	"out/ci/mac_debug_arm64",
	"--x64-out-dir",
	"out/ci/host_debug",
	"--zip"
	],
	"script": "flutter/sky/tools/create_macos_gen_snapshots.py"
	},
	{
	"name": "Profile-gen_snapshots",
	"parameters": [
	"--dst",
	"out/profile/snapshot",
	"--arm64-out-dir",
	"out/ci/mac_profile_arm64",
	"--x64-out-dir",
	"out/ci/host_profile",
	"--zip"
	],
	"script": "flutter/sky/tools/create_macos_gen_snapshots.py"
	},
	{
	"name": "Release-gen_snapshots",
	"parameters": [
	"--dst",
	"out/release/snapshot",
	"--arm64-out-dir",
	"out/ci/mac_release_arm64",
	"--x64-out-dir",
	"out/ci/host_release",
	"--zip"
	],
	"script": "flutter/sky/tools/create_macos_gen_snapshots.py"

The recipe did, however, rely on the archive_gen_snapshot rule to ensure that the underlying gen_snapshot targets were actually built. See, for example:

engine/ci/builders/mac_host_engine.json

Line 45 in e5215e6

"flutter/build/archives:archive_gen_snapshot",

A few benefits:

• Eliminates an unnecessary zip operation.
• Eliminates confusion from grepping for gen_snapshot.zip and finding the wrong location in the source.
• Grepping for create_macos_gen_snapshots will turn up the usage in the JSON build file.

Issue: flutter/flutter#151848

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or the PR is test-exempt. See testing the engine for instructions on writing and running engine tests.
• I was thoroughly confused by the fact that my changes to the contents of gen_snapshot.zip weren't showing up in the cloud bucket or tool.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[zanderso]

LGTM and to clarify, this only eliminates the unused .zip file, but the recipe is still not yet using the lipo'd gen_snapshots, correct?

[cbracken]

Yep - that's exactly correct. This is just a cleanup of dead code so the next person who has to deal with this archive has it easier.

[cbracken]

And I mean, if we're being realistic, the next person to deal with this is probably one of the people on this patch.