In clang 3.7 all functions that overrides a member function must be marked as override. If it doesn’t then compiler notifies a warning (for example: ‘Precache’ overrides a member function but is not marked ‘override’) and due to Werror compilation fails. It’s better to mark off Winconsistent-missing-override.
Clang 3.5 and Clang 3.3 are currently supported compilers, as per our Wiki. Not sure why you are using Clang 3.7, but this and, possibly other issues could possibly arise when using that specific version.
Having said that, you are welcome to help us (Linux Community) out and contribute a Pull Request to epic/master with changes that will enable use of Clang 3.7 for compiling and running the Engine.