Remove SDKROOT relative search path

This was causing warnings with the iOS 9 SDK as this path doesn't even
exist anymore and seemingly wasn't needed since XCTest came along.

Fixes #4168

[Sandbox::FileAccessor] Add C++ Sources (.i)

[Validator] build watchOS pods against watchossimulator for validation 🌈

This reverts commit c521ad1e.

Added the cocoapods-search plugin to CocoaPods

[Resolver] Allow platform detection to work for nested dependencies

[FileAccessor] Take exclude_files into account for resource_bundles

[Analyzer] Dont create cycles when computing transitive dependencies

[PodTargetInstaller] Mark all headers with availability levels

Added the cocoapods gem 'cocoapods-search' to the Gemfile
Added the dependency to the cocoapods.gemspec
Deleted the source code for search and the source code for the search specs