Fix swapping of CPUType when crossing endians

A cputype already in big endian (ex ppc) would be flipped into little
instead of staying in big, so grab the cputype in the native byte order
then flip to big if needed.

ldid.cpp

@@ -1599,8 +1599,8 @@ static void Allocate(const void *idata, size_t isize, std::streambuf &output, co
             auto &mach_header(allocation.mach_header_);
 
             fat_arch fat_arch;
-            fat_arch.cputype = Swap(mach_header->cputype);
-            fat_arch.cpusubtype = Swap(mach_header->cpusubtype);
+            fat_arch.cputype = Swap(mach_header.GetCPUType());
+            fat_arch.cpusubtype = Swap(mach_header.GetCPUSubtype());
             fat_arch.offset = Swap(uint32_t(allocation.offset_));
             fat_arch.size = Swap(uint32_t(allocation.limit_ + allocation.alloc_));
             fat_arch.align = Swap(allocation.align_);