title: Building Error: What's "-licucore" and how can I fix this error?
body: <p>After a whole day I've fixed tens of error in a legacy project, but I'm blocked by this annoying problem. I've searched a lot on the web but cannot get a relevant answer to this.     </p>
  
  <pre><code> /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: -dynamic not specified the following flags are invalid: -ObjC -ObjC 
      error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: can't locate file for: -licucore
      error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: file: -licucore is not an object file (not allowed in a library)
  </code></pre>
  
  <p>Should I modify something in Build Settings or Build Phases, or somewhere in CocoaPods???</p>
  
  <p>Add: Error happens on building a target and here are all the error info:</p>
  
  <pre><code>Libtool /Users/wangshudao/Library/Developer/Xcode/DerivedData/Diana-gfwxapulgdvudifuftotddpukijd/Build/Products/Debug-iphonesimulator/libDianaModels.a normal x86_64
  cd /Volumes/HDD/Dev/workplace/iOS/Diana
  export IPHONEOS_DEPLOYMENT_TARGET=6.1
  export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool -static -arch_only x86_64 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.2.sdk -L/Users/wangshudao/Library/Developer/Xcode/DerivedData/Diana-gfwxapulgdvudifuftotddpukijd/Build/Products/Debug-iphonesimulator -filelist /Users/wangshudao/Library/Developer/Xcode/DerivedData/Diana-gfwxapulgdvudifuftotddpukijd/Build/Intermediates/Diana.build/Debug-iphonesimulator/DianaModels.build/Objects-normal/x86_64/DianaModels.LinkFileList -ObjC -lPods-Model-AFNetworking -lPods-Model-Mantle -lPods-Model-ReactiveCocoa -lPods-Model-SSKeychain -lPods-Model-TMCache -licucore -framework AVOSCloud -framework CFNetwork -framework CoreGraphics -framework CoreLocation -framework CoreTelephony -framework Foundation -framework MobileCoreServices -framework QuartzCore -framework Security -framework SystemConfiguration -weak_framework UIKit -ObjC -lPods-Model-AFNetworking -lPods-Model-Mantle -lPods-Model-ReactiveCocoa -lPods-Model-SSKeychain -lPods-Model-TMCache -licucore -framework AVOSCloud -framework CFNetwork -framework CoreGraphics -framework CoreLocation -framework CoreTelephony -framework Foundation -framework MobileCoreServices -framework QuartzCore -framework Security -framework SystemConfiguration -weak_framework UIKit -framework SystemConfiguration -framework MobileCoreServices -framework Foundation -lPods-Model -o /Users/wangshudao/Library/Developer/Xcode/DerivedData/Diana-gfwxapulgdvudifuftotddpukijd/Build/Products/Debug-iphonesimulator/libDianaModels.a
  </code></pre>
  
  <p>/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: -dynamic not specified the following flags are invalid: -ObjC -ObjC 
  error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: can't locate file for: -licucore
  error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: file: -licucore is not an object file (not allowed in a library)
  error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: can't locate file for: -licucore
  error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: file: -licucore is not an object file (not allowed in a library)</p>