Allow disabling EarlGrey.swift installation via Cocoapods

[bootstraponline]

target 'SoGrey' do
    project 'Frameworks/SoGrey/SoGrey.xcodeproj'
    pod 'EarlGrey', '~> 1.1'
end

abstract_target 'common_ui_tests' do
    target 'TeacherUITests' do
      pod 'SwiftProtobuf', '~> 0.9.904'
      pod 'EarlGrey', '~> 1.1'
      project 'rn/Teacher/ios/Teacher.xcodeproj'
    end
end

• https://github.com/instructure/instructure-ios/blob/master/Podfile

EarlGrey.swift is provided by a shared framework SoGrey so we don't want EarlGrey.swift from the gem. You can see in the podfile, EarlGrey.swift is added to the SoGrey target. Then we have a TeacherUITests that should not have EarlGrey.swift

• https://github.com/instructure/instructure-ios/blob/master/Frameworks/SoGrey/SoGrey/EarlGrey.swift

There should be a way to tell EarlGrey to not add EarlGrey.swift on certain targets.

[bootstraponline]

The copy script also needs to be opt-out. When using a shared framework target, the copy script has the wrong framework path. There's currently no opt-out so cocoapods will inject code that breaks the tests on each pod install.