cpm_find_package Use found package version when possible (#396)

Author: robertmaynard

cmake/CPM.cmake

@@ -235,6 +235,9 @@ function(cpm_find_package NAME VERSION)
   string(REPLACE " " ";" EXTRA_ARGS "${ARGN}")
   find_package(${NAME} ${VERSION} ${EXTRA_ARGS} QUIET)
   if(${CPM_ARGS_NAME}_FOUND)
+    if(DEFINED ${CPM_ARGS_NAME}_VERSION)
+      set(VERSION ${${CPM_ARGS_NAME}_VERSION})
+    endif()
     message(STATUS "${CPM_INDENT} using local package ${CPM_ARGS_NAME}@${VERSION}")
     CPMRegisterPackage(${CPM_ARGS_NAME} "${VERSION}")
     set(CPM_PACKAGE_FOUND