[clang] [Clang][CodeGen] Use EmitLoadOfLValue instead of EmitLoadOfScalar to get LHS for complex compound assignment (PR #166798)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

Needs testcase in clang/test/CodeGen/.  Needs release note (clang/docs/ReleaseNotes.rst).

https://github.com/llvm/llvm-project/pull/166798