[clang] [Clang][AMDGPU] Accept builtins in lambda declarations (PR #135027)

[Juan Manuel Martinez Caamaño via cfe-commits]

jmmartinez wrote:

> IIRC there were bugs when you try to use lambda in conjunction with the target attribute. Can you add a test where you try to use a builtin that depends on a subtarget feature, in a function marked with the target attribute (and not available in the main compile target), that we still error?

I've added a separate test for this (the error is not triggered with -fsyntax-only but it is with -emit-llvm).

I've also added tests for local variables inside a function.

https://github.com/llvm/llvm-project/pull/135027