[MCJIT] Replace memcpy with readBytesUnaligned in RuntimeDyldMachOI386.

This should fix the failures of the MachO_i386_DynNoPIC_relocations.s test case
on MIPS hosts.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219543 91177308-0d34-0410-b5e6-96231b3b80d8