compiling 3.7.0 from source with custom libffi path

[Fetchinson .]

I'm trying to compile python 3.7.0 from source with a custom libffi
path and the compiler/linker doesn't seem to pick up the right
version. The system libffi doesn't have the development files so I've
installed the latest libffi (also from source) to /opt/custom but
still I get

INFO: Could not locate ffi libs and/or headers

Failed to build these modules:
_ctypes

Although I compile python with --prefix=/opt/custom because that's the
location I'd like to install it too. So how do I tell the build system
where to find my custom libffi?

Cheers,
Daniel



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