Download npm packages only if necessary

This makes CodeCompass installation process faster.

Fixes #456

Author: bruntib

webgui/CMakeLists.txt

@@ -18,4 +18,4 @@ install(CODE "set(CC_PACKAGE \"${CMAKE_CURRENT_SOURCE_DIR}/package.json\")")
 install(CODE "set(CC_PROFILE \"${CMAKE_CURRENT_SOURCE_DIR}/codecompass.profile.js.in\")")
 install(CODE "set(INSTALL_SCRIPTS_DIR \"${INSTALL_WEBROOT_DIR}/scripts/\")")
 install(CODE "set(CMAKE_BUILD_TYPE ${CMAKE_BUILD_TYPE})")
-install(SCRIPT InstallGUI.cmake)
+install(SCRIPT InstallGUI.cmake)

webgui/InstallGUI.cmake

@@ -4,9 +4,11 @@ execute_process(
   COMMAND cp ${CC_PACKAGE} ${INSTALL_SCRIPTS_DIR}/package.json
   WORKING_DIRECTORY ${INSTALL_SCRIPTS_DIR})
 
-execute_process(
-  COMMAND npm install
-  WORKING_DIRECTORY ${INSTALL_SCRIPTS_DIR})
+if(${CC_PACKAGE} IS_NEWER_THAN ${INSTALL_SCRIPTS_DIR}/package.json)
+  execute_process(
+    COMMAND npm install
+    WORKING_DIRECTORY ${INSTALL_SCRIPTS_DIR})
+endif()
 
 execute_process(
   COMMAND ${CMAKE_COMMAND} -E create_symlink dojo-util node_modules/util
@@ -39,4 +41,4 @@ execute_process(
 # The build-report may leak sensitive information
 file(REMOVE ${INSTALL_SCRIPTS_DIR}/release/build-report.txt)
 
-message("The Dojo Build System finished.")
+message("The Dojo Build System finished.")