cmake MPC examples

elemental/Elemental cmake/external_projects/ElMath.cmake :510 

find_package(MPC 1.0.0)

openturns/openturns CMakeLists.txt :253 

find_package (MPC)

symforce-org/symforce third_party/symengine/CMakeLists.txt :336 

find_package(MPC REQUIRED)