If by "unaffected" you mean "correct", then yes, as long as it is set up correctly for cross-compilation (I mean the compiler and assembler, which are unused on the target box in non-LTO mode).

But with GCC LTO, distcc will only distribute the parsing of the source code while the optimization and code generation will be done on the target box, so the speedup gain with distcc will be much smaller (LTO makes the ratio of work that parallelizable to work that is non-parallelizable much lower).

GCC LTO partitions the work, if it can interact with distcc it can distribute optimization too, at the cost of some missed optimizations. I don't know if that does the right thing in GCC 4.6.0