fix c-ares after introducing -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION

[kcc]

See #410 (comment)

configure: CFLAGS error: CFLAGS may only be used to specify C compiler flags, not macro definitions. 

One solution is to remove -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION from global flags and use it only in those projects there needed. (would be sad).

Another solution is to hack https://github.com/google/oss-fuzz/blob/master/projects/c-ares/build.sh to cut -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION from CFLAGS (ouch!). Let me try this first.

Also, let me ask David why is the configure script that picky...

OMG, I hate build systems.

[daviddrysdale]

AIUI you should use CPPFLAGS for preprocessor definitions, and CFLAGS for C-specific options. That way, the preprocessor options (-Iwherever -Dwhatever) can also be used in a C++ rule, without needing duplication between CFLAGS and CXXFLAGS.

Cf. http://stackoverflow.com/questions/2754966/cflags-vs-cppflags

[kcc]

Not all build systems will understand CPPFLAGS (or will they?), and only c-ares complains this way.
Do you know what is special about c-ares that it forbids the use of -DFOO in CFLAGS?

[daviddrysdale]

Looks like the check only went in a few years ago, but I don't the reasons why. c-ares does get used on a lot of obscure platforms though, so it may have been an attempt to reduce misconfigurations with odd toolsets.