Turn off Clang code-coverage generation, to avoid a link error (missing library).

There is probably a library to be linked in that would fix the link errors, but I can't see any reason for my in-project version of a library to need code coverage tests, so I'm taking the easy way out and just flipping the flag to stop the compiler from generating the code and external symbol references.
Replace "Copy Headers" phase with "Copy Files" for libocmockito target.

Static library targets ignore the Copy Headers phase, so it wasn't doing anything. But to be able to reference the headers by a logical path ("<OCMockito/xxx.h>"), we need to to copy them to the appropriate location in the Build directory, because it's rather a challenge to set up an equivalent path to the original source files when the project is included as a submodule of another project's repository.