Use _setjmp by default to use the setjmp xor cookie.
This was already done for powerpc and powerpc64 to work around a
segfault, but it seems to be a good practice on all arches.
ok gkoehler@
clang-11's __builtin_setjmp is broken, has chance of SIGSEGV during
"make build" on powerpc with ld.lld, or when passing a wrong option
(like "ruby -e" with no -e code) on powerpc64.
ok jeremy@ (maintainer)
* Disable the peephole optimizer on mips64 to avoid occasional crashes.
* Ensure sufficient alignment of builtin bytecode arrays so that
compiler.c can cast and access the data through struct ibf_header
without crashing (OpenBSD/mips64 requires strict alignment).
OK jeremy@
