prefer_static not implemented yet?

[vazub]

When building a 3rd-party project, I'd like to be able to tell it to build both library types with the -Ddefault_library=both (works) argument but link any created binaries statically, with the -Dprefer_static=true option. Unfortunately, the latter does not seem to work yet in muon, which throws an invalid option error.

Kindly request supporting such an option.