[PowerPC64] Fix broken kernel modules due to LLD 9+ TOC optimization

[alfredo]

Summary

LLD9 introduced a TOC optimization that isn't compatible with kernel dynamic linker causing panic when loading kernel modules (pf, linuxkpi and so)

This patch disables TOC optimization when building kernel modules

Test Plan

Tested kldload on powerpc64 (QEMU)

[alfredo]

removed compiler check to address gcc+lld possible use case

[jhibbits]

sys/conf/kmod.mk

172

Can't this just be:

LDFLAGS.lld+= --no-toc-optimize

?

[alfredo]

sys/conf/kmod.mk

172

I tried it in the past and it didn't work. Anyway I just double checked it and this mechanism still not working, unfortunately.

In fact, there's only one place using it (and probably isn't working too)

# grep -R "LDFLAGS.lld" /usr/src/*
stand/i386/Makefile.inc:LDFLAGS.lld+=	-Wl,--no-rosegment

[jhibbits]

Thanks for testing the alternative.

[bdragon]

Looks good to me too.