[Test Specs] Use external specs for tests

Symlink header folders by script build phase

[PathList] Simplify read_file_system implementation, deal with unicode paths

That seems to be less distracting.

[Validator] Adds space to fix typo in output in Validator

[Commands] Reorganize IPC and Lib

Before: The pattern includes header files that are not listedin source_files
After: The pattern includes header files that are not listed in source_files

[Config] Normalize installation_root to ensure same character encoding

Some characters like "ü" where being represented as `["u", "̈"]` in
ruby < 2.3 and it caused errors down the line.

[Docs] Remove vestigial comment

Update an info message for 1.x: Change xcodeproj → project

[Danger] Fail if there are merges from upstream in the PR

[Executable] fix NameError

[CopyResourcesScript] Add --target-device to ibtool invocation for XIBs #5282

[SourcesManager] Require set before using it

Update copy around updating to the latest build

[Issue Template] Update for pod env & ask for project