Resolve https://github.com/llvm/llvm-project/issues/61932. We should add the validation.
LLVM can't handle IR where subprogram definitions are nested within DICompositeType when doing LTO builds, because there's no good way to cross the CU boundary to insert a nested DISubprogram definition in one CU into a type defined in another CU.
The test cases cross-cu-inlining-2.ll and cross-cu-inlining-ranges.ll can be deleted. In the cross-cu-inlining-2.ll, the low pc and high pc of the CU are also incorrect.