当我运行npm install karma --save-dev时，大部分安装都顺利，但我收到以下错误：
make: *** [Release/obj.target/fse/fsevents.o] Error 1
gyp ERR! build error
gyp ERR! stack Error: `make` failed with exit code: 2
gyp ERR! stack at ChildProcess.onExit (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/build.js:267:23)
gyp ERR! stack at ChildProcess.emit (events.js:110:17)
gyp ERR! stack at Process.ChildProcess._handle.onexit (child_process.js:1067:12)
gyp ERR! System Darwin 12.6.0
gyp ERR! command "node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "rebuild"
gyp ERR! cwd /Volumes/myProject/node_modules/karma/node_modules/chokidar/node_modules/fsevents
gyp ERR! node -v v0.12.0
gyp ERR! node-gyp -v v1.0.2
gyp ERR! not ok
> bufferutil@1.1.0 install /Volumes/myProject/node_modules/karma/node_modules/socket.io/node_modules/engine.io/node_modules/ws/node_modules/bufferutil
> node-gyp rebuild
child_process: customFds option is deprecated, use stdio instead.
Error: Can't run /Applications/Xcode.app/usr/bin/xcodebuild (no such file).
Error: Can't run /Applications/Xcode.app/usr/bin/xcodebuild (no such file).
No receipt for 'com.apple.pkg.CLTools_Executables' found at '/'.
我在/Applications/Xcode.app/安装了XCode版本5.1.1（5B1008），但是当我在文件上显示内容时，它显示了一个名为Contents的文件夹，而没有usr目录。
您可以给出什么建议来安装gyp？