gcc6 fails to build on Leopard - illegal text relocation

[rmottola (Riccardo)]

gcc6 fails to compile, I see these warnings and errors.

:info:build ld: warning: could not create compact unwind for __Unwind_RaiseException: non-standard register 0 being saved in prolog
:info:build ld: warning: could not create compact unwind for __Unwind_ForcedUnwind: non-standard register 0 being saved in prolog
:info:build ld: warning: could not create compact unwind for __Unwind_Resume: does not use EBP or ESP based frame
:info:build ld: warning: could not create compact unwind for __Unwind_Resume_or_Rethrow: non-standard register 0 being saved in prolog
:info:build ld: illegal text-relocation to ___cpu_indicator_init in cpuinfo_s.o from anon in cpuinfo_s.o for architecture i386
:info:build collect2: error: ld returned 1 exit status
:info:build make[3]: *** [libgcc_s.dylib] Error 1

[kencu (Ken)]

as in the other similar ticket for gcc7, gcc won't build if any clang >= clang-5.0 is active.

Assembler issues relating to MacPorts modifications to cctools.