Summary:
By putting this in `fizz-config.cmake`, we can use depend on the `sodium` target without compromising our dependents ability to find the library.
Put the search module in the common location under `fbcode_builder/CMake` to let dependents use it.
Reviewed By: yfeldblum
Differential Revision: D24686041
fbshipit-source-id: 942d1ab34feef6cadac2b584eb8cb2d999bae0ca
