一个bug搞了一天发现是xcode的问题 ，娘亲，mmmp！
问题：
Can't exec "xcrun": No such file or directory at /Applications/Xcode.app/Contents/Developer/usr/bin/copypng line 17.
Use of uninitialized value $PNGCRUSH in scalar chomp at /Applications/Xcode.app/Contents/Developer/usr/bin/copypng line 18.
sh: dirname: command not found
Use of uninitialized value $args[0] in system at /Applications/Xcode.app/Contents/Developer/usr/bin/copypng line 89.
Can't exec "": No such file or directory at /Applications/Xcode.app/Contents/Developer/usr/bin/copypng line 89.
Use of uninitialized value $args[0] in join or string at /Applications/Xcode.app/Contents/Developer/usr/bin/copypng line 91.
ERROR: Failed to run -q -iphone -f 0 -rem text /Users/mac/Zenox/Quick/Pods/TYUpdater/TYUpdater/Assets/brown_gradation_s.png /Users/mac/Library/Developer/Xcode/DerivedData/Quick-gydvhfzvilecjcgshknbqtyvzjvx/Build/Products/Debug-iphonesimulator/TYUpdater/TYUpdater.bundle/brown_gradation_s.png
Command CopyPNGFile failed with a nonzero exit code
这个和网上一些其他解决方案不一样哈，这个不是代码问题哦。
解决：
两张照片解决（file->workspace setting，设置一下）
