ath: fix older clang build.

[imp]

Summary

Define NO_WUNUSED_BUT_SET_VARIABLE for clang, and use it in ATH_C to
account for different clang versions.

Sponsored by: Netflix

[kevans]

This looks correct by my eyeball, thanks!

sys/conf/kern.mk

96

Style bit: no space before = on both of these

[jhb]

The tithe isn’t quite right. This is more about fixing the build with older versions of clang, not GCC. I don’t know if we have a similar helper variable in the userland side (bad.sys.mk?). If so we should define the helper there as well.

sys/conf/kern.mk

95

I don’t think you need the else since the variable defaults to empty already?

[imp]

sys/conf/kern.mk

96

done, and fixed where I copied it from...

[jhb]

s/tithe/title/ (hate phone keyboards)

[kevans]

It occurs to me that modules/ath/Makefile should also use it, since that's likely the next failure

[imp]

In D34408#779492, @jhb wrote:

The title isn’t quite right. This is more about fixing the build with older versions of clang, not GCC. I don’t know if we have a similar helper variable in the userland side (bsd.sys.mk?). If so we should define the helper there as well.

Fixed title. We just turn off errors for this in bsd.sys.mk, so no changes are needed.

[imp]

update per reviews