[compiler-rt][hwasan] Massage prctl/arch_prctl API constants.

Move the definitions outside InitializeOsSupport(). Also remove the
undefs, as these constants won't be visible outside the .cpp file anyway.

Differential Revision: https://reviews.llvm.org/D132543

GitOrigin-RevId: c747451dc0439f0e422d99cc456575d8fa04087f
1 file changed