[ios] Add IfChange Lint annotations

Bug: none
Change-Id: I9a4f874139d13d3918a197aee0e9572453fa06ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6157727
Reviewed-by: Louis Romero <lpromero@google.com>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1403563}

docs/ios/build_instructions.md

@@ -12,11 +12,13 @@ Are you a Google employee? See
 
 ## System requirements
 
-[comment]: # (Keep the Xcode version in sync with ios/build/chrome_build.)
+<!-- LINT.IfChange -->
 
 * A 64-bit Mac capable of running the required version of Xcode.
 * [Xcode](https://developer.apple.com/xcode) 16.0 or higher.
 
+<!-- LINT.ThenChange(//ios/build/chrome_build.gni) -->
+
 Note: after installing Xcode, you need to launch it and to let it install
 the iOS simulator. This is required as part of the build, see [this discussion](
 https://groups.google.com/a/chromium.org/g/chromium-dev/c/98d6MyLoYHM/m/A_HyOGxPAgAJ)

ios/build/chrome_build.gni

@@ -9,13 +9,15 @@ import("//build/config/features.gni")
 import("//build/config/ios/config.gni")
 import("//build/config/ios/ios_sdk.gni")
 
+# LINT.IfChange
+
 # Xcode 16.0 or higher is required to build Chromium on iOS. This file should
 # only be included when building Chromium, not other related projects (cronet,
 # webrtc, ...).
-#
-# Please keep this value in sync with docs/ios/build_instructions.md.
 assert(xcode_version_int >= 1600, "Xcode 16.0 or higher is required.")
 
+# LINT.ThenChange(//docs/ios/build_instructions.md)
+
 declare_args() {
   # Disable notification center widget extensions.
   ios_enable_content_widget_extension = false