[clang] [llvm] [ARM] Emit an error when the hard-float ABI is enabled but can't be used. (PR #111334)

[Chris Copeland via cfe-commits]

chrisnc wrote:

LLVM not checking for this leads to it producing incorrect outputs given certain inputs and arguments when using `llc` and the like directly. Even in an ideal world where every frontend is target-aware and implements the rules itself (or delegates to LLVM to check before attempting to codegen), LLVM itself should still generate correct artifacts and emit an error if it's not possible to do so when invoked with invalid options.

https://github.com/llvm/llvm-project/pull/111334