To Reproduce:

1. Build & Run an empty project iOS.

2. Deploy it to device & exit Xcode.

3. Build & Run the same project (choose Append if doing it through build settings) or click CMD-B.

4. Notice that Xcode fails to build the project with:

"clang: error: linker command failed with exit code 1 (use -v to see invocation)"

5. This happens only happens when you select 'Append' when building through the build settings menu.

Because CMD-B or select Build & Run from file uses Append by default, Build & Run can only be used once with a single project unless the old project

Works fine on b14/b13.