clang whingeing about -std=c99

I've just tried building the Quagga suite using clang.

As far as I can see, it has dropped straight in as a replacement for

...except that when linking it gives me a spurious looking:

  clang: warning: argument unused during compilation: '-std=c99'

Quagga uses autoconf/automake/etc. This is configured to use
'-std=c99' for gcc, and clang is certainly looking like gcc to

I have poked around, but I cannot find an autoconf/automake way to
provide options for pre-processor and compiler phases, but not for the
linker phase.

Am I stuck here ? Is there a -Wno-whinge-about-unused-arguments ?

The linker is being given a bunch of -W and what not arguments that I
doubt it needs... why whinge about -std=c99 in particular ?