x86 uses offset 1 while most RISC architectures use offset 4.
Check x86 first to prevent changes for new RISC architectures.
For sancov, getPreviousInstructionPc does not use the PC - 8 code path for
Sparc. Triple.h does not have isSparc yet and I hope someone can investigate
why Mips/Sparc use the weird -8.