What build flags are available for brew install of gcc?

What build flags are available for brew install of gcc?

I'm curious as to what build flags are available to me when installing gcc
4.8 using brew.
This question explains how to install gcc 4.8 using brew, but only
specifies two possible flags i.e (--enable-cxx and --enable-fortran).
Is there a list of what's available or can someone iterate them for me?
If it matters I am running OS X 10.7.5 on the Intel i5 dual core.