Add remill and gap portfiles

[xlauko]

Add remill and gap ports.

remill port allows to specify features cxx-common-llvm-14 or system-llvm to build with local install llvm or uses cxx-common provided LLVM.

[ekilmer]

I think I mentioned this already privately, but ideally we use a commit on master branch before merging this

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
4 out of 5 committers have signed the CLA.

✅ ekilmer
✅ xlauko
✅ Ninja3047
✅ PappasBrent
❌ lkorenc
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