[BOLT] Fix stack alignment for runtime lib

Summary:
Right now, the SAVE_ALL sequence executed upon entry of both
of our runtime libs (hugify and instrumentation) will cause the stack to
not be aligned at a 16B boundary because it saves 15 8-byte regs. Change
the code sequence to adjust for that. The compiler may generate code
that assumes the stack is aligned by using movaps instructions, which
will crash.

(cherry picked from FBD22744307)