Adding extra C compiler arguments when building with hadrian?

[Ömer Sinan Ağacan]

In make build system I can add extra C compiler arguments to any flavor using
something like

    BuildFlavour = ...

    ifneq "$(BuildFlavour)" ""
    include mk/flavours/$(BuildFlavour).mk
    endif

    GhcRtsHcOpts += -O0 -g3

How do I do the same in hadrian when defining a flavor?

Thanks,

Ömer