We only had to pile everything into the src/fuzzing/firmware directory
because honggfuzz could not cope with more than one input path.
This way each plugin is self contained and easy to copy.
Also, install the fuzzing builder objects as this fixes the installed
tests when srcdir does not exist.
Based on a patch by Jan Tojnar <jtojnar@gmail.com>, many thanks.
This makes a lot more sense; we can parse a firmware and export the same XML
we would use in a .builder.xml file. This allows us to two two things:
* Check we can round trip from XML -> binary -> XML
* Using a .builder.xml file we can check ->write() is endian safe
