As a temporary measure, use an ultra-evil sledgehammer method to silence the
PACKAGE_FOO clashes. The correct way of doing this would be splitting up
HsPACKAGE.h and ghcconfig.h into two parts each: One part would be generated by
autoheader and would contain the defines which are needed during package build
time only. The other part would contain all kinds of stuff which is needed for
using the given package (no PACKAGE_FOO defines here). For an example of this,
see the OpenAL package. As an additional benefit, this would keep the namespace
much cleaner, because 2nd kind of headers is typically smaller.

No time for the real thing currently, hope the current workaround works...