packer: embed entitlements in simulator binaries like Xcode

[chintan100]

What does this PR do?

Fixes #83. Simulator builds now get their entitlements the way Xcode does it: linked into the binary's __TEXT,__entitlements (XML) and __TEXT,__ents_der (DER) sections, with no entitlements in the ad-hoc code signature.

Today xtool dev also puts entitlements in the ad-hoc signature for simulator builds. With restricted entitlements (e.g. keychain-access-groups, com.apple.developer.healthkit) the app fails to launch on the simulator ("Simulator device failed to launch …").

• Packer writes <target>-Simulated.xcent and .xcent.der next to the builder package and passes -sectcreate __TEXT __entitlements … / -sectcreate __TEXT __ents_der … to the linker, the same flags Xcode uses.
• New EntitlementsDER encodes entitlements in the format codesign --generate-entitlement-der produces.
• PackOperation skips ad-hoc signing with entitlements for simulator builds (Xcode signs these with {}). Device builds are unchanged.
• Unlike Xcode, this doesn't add application-identifier, since xtool doesn't know the team prefix for simulator builds.

How was it tested?

• Unit tests: the DER encoder matches codesign --generate-entitlement-der output byte-for-byte (booleans, integers including 1 and -1, strings, arrays, nested dictionaries), and Packer emits the flags and files only for simulator triples.
• On macOS (Xcode 27, Swift 6.4, iOS 26.5 simulator), with an app using com.apple.security.application-groups, keychain-access-groups and com.apple.developer.healthkit: on main it fails to launch; with this PR it launches, the app group container resolves, and SecItemAdd into the shared keychain group succeeds, the same as the Xcode-built app.
• Device builds are unchanged: no sections, and entitlements are still in the signature.
• swift test and make lint pass (XTL_CI=1).
• Not tested: app extension targets end to end (same code path), and Linux, where linking relies on ld64.lld supporting -sectcreate.

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Summary by CodeRabbit

• New Features
  • Simulator builds now include entitlement data for supported apps and extensions, with the required linker settings.
  • Build settings distinguish simulator from device builds, selecting the corresponding platform output.
• Bug Fixes
  • Simulator builds no longer attempt entitlement signing; device builds continue to use the existing signing behavior.

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ℹ️ Recent review info

⚙️ Run configuration

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📥 Commits

Reviewing files that changed from the base of the PR and between c045686 and aa1588e.

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📒 Files selected for processing (1)

• Sources/PackLib/EntitlementsDER.swift

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🚧 Files skipped from review as they are similar to previous changes (1)

• Sources/PackLib/EntitlementsDER.swift

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📝 Walkthrough

Walkthrough

Simulator builds now generate XML and DER entitlement files and pass linker flags for entitlement sections. They skip entitlement signing. The DER encoder supports booleans, integers, strings, arrays, and dictionaries.

Changes

Simulator Entitlements

Layer / File(s)	Summary
Entitlement DER encoding Sources/PackLib/EntitlementsDER.swift, Tests/XToolTests/SimulatorEntitlementsTests.swift	The encoder converts supported property-list values to DER. Tests compare its output with fixed codesign-generated bytes.
Simulator build integration Sources/PackLib/BuildSettings.swift, Sources/PackLib/Packer.swift, Sources/XToolSupport/DevCommand.swift, Tests/XToolTests/SimulatorEntitlementsTests.swift	Simulator detection controls entitlement file generation, linker settings, and platform selection. Simulator builds skip the entitlement-signing block. Tests check generated files and simulator and device linker flags.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Packer
  participant EntitlementsDER
  participant GeneratedTarget
  Packer->>EntitlementsDER: Encode entitlement property list
  EntitlementsDER-->>Packer: Return DER bytes
  Packer->>GeneratedTarget: Add entitlement files and linker section flags

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Merge Risk: ⚪ Minimal · up to aa158

This change embeds entitlements in simulator binaries, and the supplied context shows no unresolved merge-blocking risk. The earlier decoding-error concern has been addressed. App extensions and Linux linking were not tested end to end, which is a normal validation gap and not an identified defect.

Pre-merge checks | 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: embedding entitlements in simulator binaries to match Xcode behavior.
Linked Issues check		Issue [#83] requires simulator entitlements in linker-created sections. Packer.simulatorEntitlementsFlags(in:) writes XML and DER entitlement files and adds -sectcreate flags for `__TEXT,__entitle…
Out of Scope Changes check		The changes remain within issue [#83]. EntitlementsDER, simulator detection, linker flag generation, simulator signing behavior, app-extension linker support, and tests support simulator entitlement…

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @Sources/PackLib/EntitlementsDER.swift:
- Around line 13-26: Update Value.init(from:) to decode dictionaries
conditionally instead of letting dictionary decoding produce a generic
type-mismatch error. If none of the supported types decode, throw
DecodingError.dataCorruptedError with a description identifying the unsupported
entitlement value type.

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ℹ️ Review info

⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: CHILL
• Plan: Advanced
• Run ID: 2fea5b3b-9c28-4699-9d02-423aeba4966d

📥 Commits

Reviewing files that changed from the base of the PR and between d802c71 and c045686.

📒 Files selected for processing (5)

• Sources/PackLib/BuildSettings.swift
• Sources/PackLib/EntitlementsDER.swift
• Sources/PackLib/Packer.swift
• Sources/XToolSupport/DevCommand.swift
• Tests/XToolTests/SimulatorEntitlementsTests.swift

Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 7 remain after this review.