iOS Enrollment integration test fails to build: untrusted Swift macro (ModifiedCopy)

[jaredlockhart]

Problem

The iOS Enrollment integration test fails at the "Build Fennec scheme" step (the enrollment test itself never runs). Surfaced on the automated iOS-SHA bump PR #15894.

Build error:

ModifiedCopyMacro/Package.swift: error: Macro "ModifiedCopyMacros" from package "ModifiedCopy" must be enabled before it can be used
** BUILD FAILED **  (exit code 65)

A newer firefox-ios main pulled in a dependency on the ModifiedCopy Swift macro package. Since Swift 5.9, third-party macros run arbitrary code at compile time and must be explicitly trusted before they compile — interactive Xcode shows a "Trust & Enable" prompt, but non-interactive xcodebuild in CI just fails. This is a recurring class: every new compile-time macro package in firefox-ios will fail the auto-bump PR the same way until CI is told to trust macros.

Fix

Add -skipMacroValidation to the xcodebuild build invocation in .github/workflows/ios-integration-test.yml. This bypasses the trust check on macros from the firefox-ios source we just checked out; it has no effect on what the enrollment test validates.

Acceptance criteria

• The xcodebuild build step in the iOS integration workflow skips macro fingerprint validation.
• The iOS Enrollment integration test builds Fennec and runs the enrollment test to completion.

┆Issue is synchronized with this Jira Task