[clang] [NFC][clang] Split clang/lib/CodeGen/CGBuiltin.cpp into target-specific files (PR #132252)

[Benjamin Maxwell via cfe-commits]

================
@@ -0,0 +1,8530 @@
+//===------ AArch64.cpp - Emit LLVM Code for builtins ---------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This contains code to emit Builtin calls as LLVM code.
+//
+//===----------------------------------------------------------------------===//
+
----------------
MacDue wrote:

Not a strong opinion, but this appear to handle both ARM and AArch64, which is similar to `SemaARM`, so maybe this would be more consistent if named just `ARM`?

https://github.com/llvm/llvm-project/pull/132252