While these files are generated they don't really change and are not
architecture dependant. The previous solution prevented cross-compilation
from the repository as `bliss_huffman` was built for the target system but
was then executed on the build host to create the source files, which
naturally was bound to fail.
The `recreate-bliss-huffman` make target can be used inside the bliss
directory to update the source files if needed.
Fixes#812.
This requires moving test files so that the Makefile for the tests can be
included after building libstrongswan, which requires the plugin when
building monolithically. Due to this a static helper library is required
as directly referring to object files (or source files) is not possible.
It's also necessary to avoid any link-time dependency on libstrongswan in
bliss_huffman, to avoid circular dependencies (bliss_huffman -> libstrongswan
-> bliss -> bliss_huffman).
By pre-multiplying the input arrays with a linear phase the
fast multiplication via FFT and inverse FFT computes a negative
wrapped convolution corresponding to a modulus of x^n+1.
Tobias Brunner