Right. It wasn't clear at the beginning but now I understand your point. Regular LTO (by design) doesn't support concurrency nor does it support incremental builds. OTOH ThinLTO supports both.
CMake CMAKE_INTERPROCEDURAL_OPTIMIZATION variable, when set, opts in for LTO so, yes, due to LTO design you will inherently lose concurrent linkage.
CMake CMAKE_INTERPROCEDURAL_OPTIMIZATION variable, when set, opts in for LTO so, yes, due to LTO design you will inherently lose concurrent linkage.