message: pass in install prefix path to external-projects
  Summary:
  This adds path of newly built dependencies so that 'external-projects' such as
  fizz can find them
diff: # LICENSE file in the root directory of this source tree.
  include(ExternalProject)
  +list(APPEND PREFIX_PATH ${CMAKE_PREFIX_PATH} ${CMAKE_INSTALL_PREFIX})
  # Construct platform aware cmake args since on OSX
  # it requires path to the openssl libs
  list(APPEND CMAKE_ARGS
  -DCMAKE_BUILD_TYPE:STRING=RelWithDebInfo
  - -DCMAKE_PREFIX_PATH:STRING=${CMAKE_PREFIX_PATH}
  + -DCMAKE_PREFIX_PATH:STRING=${PREFIX_PATH}
  )
  if(UNIX AND APPLE)
  list(APPEND CMAKE_ARGS
  