Since this repo contains derivative files from a bunch of other software, every dependency's directory will probably need a copy of corresponding upstream license file (in case the project files are derived from upstream) or third-party license file (in case the project files are derived from some other place, like harfbuzz and gettext-runtime), which will clarify license of that particular dependency + copyrights.

If that is too much effort (and I think it is), at the very least there should be an assertion somewhere (eg in the README) that our license + copyright only applies to build.ps1, etc. and the individual dependencies' files are under their own license + copyright.