apply_patches CMakeFunction shouldn't checkout existing branch

Function "apply_patches" checks out the branch, where patches are applied if it already exists:
https://github.com/intel/opencl-clang/blob/51fd5b94830ebdc2c618da24217d08a27de9ca36/cmake/modules/CMakeFunctions.cmake#L71

I think the logic here might lead to unexpected issues, e.g. if you download new opencl-clang commit, where a new patch is introduced, it won't be applied if the branch is not manually deleted.

Maybe the function should delete the branch at first step?

Start at apply_patches in cmake/modules/CMakeFunctions.cmake around line 71 and inspect how an existing branch is handled before patches are applied. Confirm the behavior when a new opencl-clang commit adds a patch, then ensure the function does not leave that patch unapplied when the branch already exists.

Written by the indexing model from the issue text.