Replace nop with ret sled on ARM64
Replace nop with ret sled on ARM64

Instead of running through 64 nops on average, every instruction in the
trampoline now jumps directly to the end of the function.

CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer,CodeIntelligenceTesting/jazzer