cmake: don't add CMAKE_INSTALL_PREFIX for mroonga bundled build

Because CPack packaging process fails.

CMakeLists.txt

@@ -44,9 +44,14 @@ set(LIB_DIR "lib")
 set(INCLUDE_DIR "include")
 set(GRN_INCLUDE_DIR "include/groonga")
 set(DATA_DIR "share")
-set(GRN_DATA_DIR "${CMAKE_INSTALL_PREFIX}/${DATA_DIR}/${GRN_PROJECT_NAME}")
 set(CONFIG_DIR "etc")
-set(GRN_CONFIG_DIR "${CMAKE_INSTALL_PREFIX}/${CONFIG_DIR}/${GRN_PROJECT_NAME}")
+if (CMAKE_CURRENT_SOURCE_DIR MATCHES "mroonga/vendor/groonga$")
+  set(GRN_DATA_DIR "${DATA_DIR}/${GRN_PROJECT_NAME}")
+  set(GRN_CONFIG_DIR "${CONFIG_DIR}/${GRN_PROJECT_NAME}")
+else()
+  set(GRN_DATA_DIR "${CMAKE_INSTALL_PREFIX}/${DATA_DIR}/${GRN_PROJECT_NAME}")
+  set(GRN_CONFIG_DIR "${CMAKE_INSTALL_PREFIX}/${CONFIG_DIR}/${GRN_PROJECT_NAME}")
+endif()
 
 set(GRN_LOG_PATH
   "${CMAKE_INSTALL_PREFIX}/var/log/${GRN_PROJECT_NAME}/${GRN_PROJECT_NAME}.log"
@@ -69,8 +74,13 @@ set(GRN_STACK_SIZE
   "DANGER!!! groonga stack size. Normarlly, you should not change this variable.")
 set(GRN_RELATIVE_PLUGINS_DIR
   "${GRN_PROJECT_NAME}/plugins")
-set(GRN_PLUGINS_DIR
-  "${CMAKE_INSTALL_PREFIX}/${LIB_DIR}/${GRN_RELATIVE_PLUGINS_DIR}")
+if (CMAKE_CURRENT_SOURCE_DIR MATCHES "mroonga/vendor/groonga$")
+  set(GRN_PLUGINS_DIR
+    "${LIB_DIR}/${GRN_RELATIVE_PLUGINS_DIR}")
+else()
+  set(GRN_PLUGINS_DIR
+    "${CMAKE_INSTALL_PREFIX}/${LIB_DIR}/${GRN_RELATIVE_PLUGINS_DIR}")
+endif()
 set(GRN_PLUGIN_SUFFIX "${CMAKE_SHARED_MODULE_SUFFIX}")
 set(GRN_DLL_FILENAME
   "${CMAKE_SHARED_LIBRARY_PREFIX}groonga${CMAKE_SHARED_LIBRARY_SUFFIX}")