How to use the cmake.__version__.split function in cmake

if gmxapi_DIR != os.path.commonpath([gmxapi_DIR, gmx_toolchain]):
    raise GmxapiInstallError('GROMACS toolchain file {} is not in gmxapi_DIR {}'.format(
        gmx_toolchain,
        gmxapi_DIR
    ))

cmake_platform_hints = ['-DCMAKE_TOOLCHAIN_FILE={}'.format(gmx_toolchain)]

# TODO: Use package-specific hinting variable.
# We want to be sure that we find a -config.cmake associated with the
# toolchains file, but we want to preempt most of the normal CMake
# [search procedure](https://cmake.org/cmake/help/latest/command/find_package.html#id5),
# which could lead to hard-to-diagnose build problems.
# Note that _ROOT is not standard until CMake 3.12
# Reference https://cmake.org/cmake/help/latest/policy/CMP0074.html#policy:CMP0074
_cmake_major, _cmake_minor = cmake.__version__.split('.')[0:2]
if int(_cmake_major) >= 3 and int(_cmake_minor) >= 12:
    cmake_gmxapi_hint = '-Dgmxapi_ROOT={}'
else:
    cmake_gmxapi_hint = '-DCMAKE_PREFIX_PATH={}'
cmake_gmxapi_hint = cmake_gmxapi_hint.format(gmxapi_DIR)

cmake_args = list(cmake_platform_hints)
cmake_args.append(cmake_gmxapi_hint)

setup(
    name='gmxapi',

    # TODO: (pending infrastructure and further discussion) Replace with CMake variables from GMXAPI version.
    version='0.1.0b2',
    python_requires='>=3.5, <3.9',
    setup_requires=['cmake>=3.9.6',