This makes -fsanitize=kernel-address emit the correct globals
constructors for the kernel. We had to do the following:
- Disable generation of constructors that rely on linker features such as dead-global elimination.
- Only emit constructors for globals *not* in explicit sections. The kernel uses sections for special globals, which we should not touch.
- With 'clang/test/CodeGen/asan-globals.cpp'.
- With test_kasan.ko, we can see:
BUG: KASAN: global-out-of-bounds in kasan_global_oob+0xb3/0xba [test_kasan]