[clang] [clang-tools-extra] [llvm] [AArch64] Implement -fno-plt for SelectionDAG/GlobalISel (PR #78890)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> It looks like some of the tests might be failing? Or does it need a rebase?

Sorry about it. The last minute `FastISel` change caused some failures. `Addr.getGlobalValue()` could be null. I have simplified `AArch64FastISel.cpp` to just check `"RtLibUseGOT"` (added by `-fno-plt`) and fixed the failures.

https://github.com/llvm/llvm-project/pull/78890