Include subproject.cmake

CMake/subproject.cmake

@@ -0,0 +1,20 @@
+function(add_subproject name)
+   if(ARGC GREATER 1)
+      set(package_name ${ARGV1})
+   else()
+      set(package_name ${name})
+   endif()
+
+   if(TARGET ${name})
+      message("Subproject ${name} already included, skipping")
+   else()
+      find_package(${package_name} QUIET)
+      string(TOUPPER ${package_name} upper)
+      if(NOT SOURCE_${upper} AND ${upper}_FOUND)
+         message("Found ${package_name} on system")
+      else()
+         message("Adding ${name} as subdirectory")
+         add_subdirectory(${name} EXCLUDE_FROM_ALL)
+      endif()
+   endif()
+endfunction()