investigate Apple OpenCL runtime usability
A user report seems to indicate that some versions of Apple OpenCL runtime are buggy which also is supported by the fact that the OpenMM project warned about similar issues (although quite some time ago).
In the above linked thread a user reports that the OpenMM-relevant bugs were fixed recently, so that flags OS X versions >10.7.4 <10.10.3. as possibly problematic for GROMACS too.
Prevent AMD OpenCL on OS X prior to 10.10.4
OS X release 10.9.x has been confirmed to produce invalid OpenCL
kernels for AMD (but correct for NVIDIA), and we have tested that
it is fixed in 10.10.4. The fix might actually have appeared
already in 10.10.3, but it's not worth tracking down the exact
point since 10.10.5 is already out.
This change will issue a CMake warning when compiling GROMACS
on earlier OS X releases, and at runtime we check the version
again and mark AMD GPUs as incompatible.
Also fixed docs about the length of time JIT compilation takes