An earlier version of #16546 used both --with-boost-process and --enable-external-signer, which was simplified to only use the latter. However I forgot to update CI, so the external signer tests were not run.
This package is currently installed as a side-effect of installing our
other libboost-*-dev packages. However as those continue to dissapear,
it makes sense to install boost dev explicitly.
Fuzzing code uses C++17 specific code (e.g. std::optional), so it is not
possible to compile with --enable-fuzz and without --enable-c++17.
Thus, turn on --enable-c++17 whenever --enable-fuzz is used.
Sjors Provoost