powerpc64*: workaround for broken binaries generated with llvm12

[alfredo]

Summary

powerpc64 and powerpc64 binaries are crashing with segmentation fault when -fstack-protector-strong is used with any optimization level. The binaries seem correct if one of -fstack-protector or -O[0|1|2|3] is ommited.

This patch add a temporary workaround while root cause is being investigated.

MFC after: 1 day

Test Plan

buildworld + chroot
run binaries like clang, ld.lld, llvm-objdump, ls, cp, echo

[emaste]

is there a PR to reference here?

[alfredo]

Move logic to BROKEN_OPTIONS as suggested by @jhibbits

[alfredo]

In D31646#713717, @emaste wrote:

is there a PR to reference here?

A PR against LLVM? Not yet. I reduced it to a test program available at https://people.freebsd.org/~alfredo/tmp/llvm12_crash/. I should file a PR later today.
On FreeBSD side there a report from a user on freebsd-ppc mailing list: https://lists.freebsd.org/archives/freebsd-ppc/2021-August/000035.html

[emaste]

Move logic to BROKEN_OPTIONS as suggested by @jhibbits

This will work for src itself, but I think it won't work with ports that use /usr/share/mk?

[alfredo]

In D31646#713731, @emaste wrote:

Move logic to BROKEN_OPTIONS as suggested by @jhibbits

This will work for src itself, but I think it won't work with ports that use /usr/share/mk?

I talked to @pkubaj on IRC, he should take care of ports side after this patch is commited

[alfredo]

Abandoned in favor of D31698