Move common functions shared by TableGen Option Emitter
and Options library to Support:
- Move `StrCmpOptionName` and base it on the existing version
in OptTable.cpp, with an additional mode to control fall back to
case insensitive comparison.
- Add `StrCmpOptionPrefixes` to compare prefixes and use zip() to
iterate through lists of prefixes.
- Rename `CompareOptionRecords` to less ambiguous name
`IsOptionRecordLess`.
- Merge 2 back-to-back ifs with same condition in
`IsOptionRecordLess`.
Fixes https://github.com/llvm/llvm-project/issues/107723
Handle the case of same pointer used as both inputs to the
`CompareOptionRecords`, to avoid emitting errors for equivalent options.
Follow-up to #107696.
Refactor of the llvm-tblgen source into:
- a "Basic" library, which contains the bare minimum utilities to build
`llvm-min-tablegen`
- a "Common" library which contains all of the helpers for TableGen
backends. Such helpers can be shared by more than one backend, and even
unit tested (e.g. CodeExpander is, maybe we can add more over time)
Fixes#80647
