[vcpkg_script] Customize port configure variables (CMake) from triplet.

[Neumann-A]

Nice feature to have to change the configure options via the triplet file instead of touching the portfile. Currently only additional compiler flags can be set if I read the scripts correctly.

[cbezault]

@Neumann-A it's not exactly clear to me what you're trying to describe here.
What variables are you trying to customize from the triplet?

[Neumann-A]

something like VCPKG_CMAKE_ADDITIONAL_OPTIONS which passes additional options to cmake based ports in the configure step. (Just like VCPKG_CXX_FLAGS allows passing extra CXX_FLAGS)

[cbezault]

So effectively cmake defaults?