Spack configuration

[jwallwork23]

Closes #122.

This PR provides a development spack.yaml configuration file to install FTorch's dependencies.

It also sets up a workflow for building a Docker image with this Spack setup inside it and hooks it up in the CI. The workflow is triggered either when a relevant file is changed or at the start of every third month.

[jwallwork23]

Seems to all be set up although the CI hits a linking error for pFUnit

-- Building with Fortran PyTorch coupling
-- Configuring done (1.8s)
-- Generating done (0.1s)
-- Build files have been written to: /__w/FTorch/FTorch/src/build
[  3%] Building Fortran object CMakeFiles/ftorch.dir/ftorch.F90.o
[  6%] Building Fortran object CMakeFiles/ftorch.dir/ftorch_test_utils.f90.o
[ 10%] Building CXX object CMakeFiles/ftorch.dir/ctorch.cpp.o
[ 13%] Linking CXX shared library libftorch.so
[ 13%] Built target ftorch
[ 16%] Generating test_tensor_constructors.F90
Processing file ../../../test/unit/test_tensor_constructors.pf
 ... Done.  Results in test_tensor_constructors.F90
[ 20%] Building Fortran object test/unit/CMakeFiles/test_tensor_constructors.dir/test_tensor_constructors.F90.o
[ 23%] Building Fortran object test/unit/CMakeFiles/test_tensor_constructors.dir/test_tensor_constructors_driver.F90.o
[ 26%] Linking Fortran executable test_tensor_constructors
/usr/bin/ld: /opt/view/PFUNIT-4.7/lib/libfunit.a: error adding symbols: archive has no index; run ranlib to add one
collect2: error: ld returned 1 exit status
gmake[2]: *** [test/unit/CMakeFiles/test_tensor_constructors.dir/build.make:120: test/unit/test_tensor_constructors] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:265: test/unit/CMakeFiles/test_tensor_constructors.dir/all] Error 2
gmake: *** [Makefile:146: all] Error 2

[jwallwork23]

Also note that the Docker image is fairly chunky. This is mainly due to intel-openapi-mkl getting pulled in as a dependency for Spack's py-torch package. I haven't figured out if it's possible to avoid this yet.

REPOSITORY                              TAG       IMAGE ID       CREATED        SIZE
ghcr.io/cambridge-iccs/ftorch-dev-env   latest    8cbb021b754b   14 hours ago   6.61GB

[jwallwork23]

Also note that the Docker image is fairly chunky. This is mainly due to intel-openapi-mkl getting pulled in as a dependency for Spack's py-torch package. I haven't figured out if it's possible to avoid this yet.

REPOSITORY                              TAG       IMAGE ID       CREATED        SIZE
ghcr.io/cambridge-iccs/ftorch-dev-env   latest    8cbb021b754b   14 hours ago   6.61GB

This has now been reduced significantly, thanks @TomMelt!

REPOSITORY                              TAG       IMAGE ID       CREATED             SIZE
ghcr.io/cambridge-iccs/ftorch-dev-env   latest    c485b6483a61   About an hour ago   1.85GB