[lldb][LoongArch] Preserve temporary symbols starting with `.L` in lldb symbol table
LoongArch64 always uses symbols for relocations, so temporary symbols
starting with ".L" should be preserved so that relocations in
`.debug_info` can be fixed correctly.
After this commit, three tests passed:
```
lldb-shell :: SymbolFile/DWARF/anon_class_w_and_wo_export_symbols.ll
lldb-shell :: SymbolFile/DWARF/clang-ast-from-dwarf-unamed-and-anon-structs.cpp
lldb-shell :: SymbolFile/DWARF/clang-gmodules-type-lookup.c
```