[clang] [clang-tools-extra] [compiler-rt] [flang] [lld] [lldb] [llvm] [mlir] [openmp] [pstl] Finally formalise our defacto line-ending policy (PR #86318)

[Saleem Abdulrasool via cfe-commits]

compnerd wrote:

> changes to `clang/test/CXX/lex/lex.literal/lex.string/p4.cpp` should be reverted (it's a CRLF related test)

This is the type of problems that I am concerned about. We certainly have some tests which are line-ending sensitive, and each test should be audited before we make such a change.

https://github.com/llvm/llvm-project/pull/86318