Stop leaking temporary nodes from `DIBuilder::createCompileUnit()`.
`replaceAllUsesWith()` doesn't delete the nodes, so we need to delete
them "manually" (well, `TempMDTuple` does that for us).
Similarly, stop leaking the temporary nodes used for variables of
subprograms.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234617 91177308-0d34-0410-b5e6-96231b3b80d8