Build issue on older CMake

[nigelsim]

I'm trying to use wmm2020 within a containerised app, but I'm hitting a failure under some build conditions, so I'm documenting these here so it may help others, and maybe there is an opportunity to tighten up the dependency ranges.

When I build with CMake 3.13.4 using the following:

FROM python:3.9-slim-buster
RUN apt-get update && apt-get install -y python3-dev cmake \
    && rm -rf /var/lib/apt/lists/* \
    && pip install --no-cache-dir --upgrade setuptools \
    && pip install --no-cache-dir . \
    && python -c 'import wmm2020' \
    && apt-get remove -y --purge python3-dev cmake \
    && apt-get autoremove -y

I get

...
SetCTestConfiguration:BuildDirectory:/usr/local/lib/python3.9/site-packages/wmm2020/build
SetCTestConfiguration:SourceDirectory:/usr/local/lib/python3.9/site-packages/wmm2020
Cannot instantiate test handler ctest_build
has no project to build. If this is a "built with CMake" project, verify that CTEST_CMAKE_GENERATOR and CTEST_PROJECT_NAME are set.
CTEST_PROJECT_NAME is usually set in CTestConfig.cmake. Verify that CTestConfig.cmake exists, or CTEST_PROJECT_NAME is set in the script, or PROJECT_NAME is passed as an argument to ctest_build.
Alternatively, set CTEST_BUILD_COMMAND to build the project with a custom command line. error from command
CMake Error at /usr/local/lib/python3.9/site-packages/wmm2020/setup.cmake:107 (message):
  Build and test failed.


-- SKIP: ctest_test(): returncode: 0; CMake error code: -1
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/wmm2020/__init__.py", line 1, in <module>
    from .base import wmm, wmm_point
  File "/usr/local/lib/python3.9/site-packages/wmm2020/base.py", line 16, in <module>
    build()
  File "/usr/local/lib/python3.9/site-packages/wmm2020/build.py", line 23, in build
    subprocess.check_call([exe, "-S", str(file), "-VV"])
  File "/usr/local/lib/python3.9/subprocess.py", line 373, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/bin/ctest', '-S', '/usr/local/lib/python3.9/site-packages/wmm2020/setup.cmake', '-VV']' returned non-zero exit status 255.

However, building with a newer distro and CMake 3.18.4

FROM python:3.9-slim-bullseye
RUN apt-get update && apt-get install -y python3-dev cmake \
    && rm -rf /var/lib/apt/lists/* \
    && pip install --no-cache-dir --upgrade setuptools \
    && pip install --no-cache-dir . \
    && python -c 'import wmm2020' \
    && apt-get remove -y --purge python3-dev cmake \
    && apt-get autoremove -y

Everything builds fine.