Handle no-target case through a user information.

Lean implementation.

Config.cmake.in

@@ -108,7 +108,7 @@ IF(COMMAND ADD_REQUIRED_DEPENDENCY)
   ENDFOREACH()
 ENDIF(COMMAND ADD_REQUIRED_DEPENDENCY)
 
-include("${CMAKE_CURRENT_LIST_DIR}/@[email protected]")
+@INCLUDE_TARGETS_FILE@
 
 foreach(component ${@PROJECT_NAME@_FIND_COMPONENTS})
   set(comp_file "${CMAKE_CURRENT_LIST_DIR}/${component}Config.cmake")

package-config.cmake

@@ -154,6 +154,13 @@ if(_PKG_CONFIG_REQUIRES)
   endforeach()
   list(REMOVE_DUPLICATES _PKG_CONFIG_REQUIRES_LIST)
 endif(_PKG_CONFIG_REQUIRES)
+
+if(NOT ${PROJECT_NAME}_ZERO_TARGET)
+  SET(INCLUDE_TARGETS_FILE "include(\"\${CMAKE_CURRENT_LIST_DIR}/${TARGETS_EXPORT_NAME}.cmake\")")  
+else()
+  SET(INCLUDE_TARGETS_FILE "# Package with no targets")
+endif()
+
 configure_package_config_file(
     "cmake/Config.cmake.in"
     "${PROJECT_CONFIG}"
@@ -170,11 +177,14 @@ install(
 
 # Config
 #   * <prefix>/lib/cmake/Foo/FooTargets.cmake
-install(
+if(NOT ${PROJECT_NAME}_ZERO_TARGET)
+  install(
     EXPORT "${TARGETS_EXPORT_NAME}"
     NAMESPACE "${namespace}"
     DESTINATION "${CONFIG_INSTALL_DIR}"
-)
+    )
+endif()
+
 ENDMACRO(SETUP_PROJECT_PACKAGE_FINALIZE)
 
 #.rst: