Use INTERFACE library for petsird

[KrisThielemans]

#161 created a petsird library for convenience of using it.

As there are no actual source files in the library at the moment, I tried the following

add_library(petsird INTERFACE)
target_link_libraries(petsird INTERFACE petsird_generated)
target_include_directories(petsird INTERFACE "${PROJECT_SOURCE_DIR}/generated")

but this failed with linking errors

: && /home/sirfuser/mambaforge/envs/prd/bin/x86_64-conda-linux-gnu-c++ -fvisibility-inlines-hidden -fmessage-length=0 -march=nocona -mtune=haswell -ftree-vectorize -fPIC -fstack-protector-strong -fno-plt -O2 -ffunction-sections -pipe -isystem /home/sirfuser/mambaforge/envs/prd/include -Wl,-O2 -Wl,--sort-common -Wl,--as-needed -Wl,-z,relro -Wl,-z,now -Wl,--disable-new-dtags -Wl,--gc-sections -Wl,--allow-shlib-undefined -Wl,-rpath,/home/sirfuser/mambaforge/envs/prd/lib -Wl,-rpath-link,/home/sirfuser/mambaforge/envs/prd/lib -L/home/sirfuser/mambaforge/envs/prd/lib helpers/CMakeFiles/petsird_generator.dir/petsird_generator.cpp.o -o helpers/petsird_generator  /home/sirfuser/mambaforge/envs/prd/lib/libhdf5.so  /home/sirfuser/mambaforge/envs/prd/lib/libcrypto.so  /home/sirfuser/mambaforge/envs/prd/lib/libcurl.so  -lpthread  /home/sirfuser/mambaforge/envs/prd/lib/libsz.so  /home/sirfuser/mambaforge/envs/prd/lib/libz.so  /home/sirfuser/mambaforge/envs/prd/x86_64-conda-linux-gnu/sysroot/usr/lib/libdl.so  /home/sirfuser/mambaforge/envs/prd/x86_64-conda-linux-gnu/sysroot/usr/lib/libm.so  /home/sirfuser/mambaforge/envs/prd/lib/libhdf5_cpp.so  /home/sirfuser/mambaforge/envs/prd/lib/libhdf5.so  /home/sirfuser/mambaforge/envs/prd/lib/libcrypto.so  /home/sirfuser/mambaforge/envs/prd/lib/libcurl.so  -lpthread  /home/sirfuser/mambaforge/envs/prd/lib/libsz.so  /home/sirfuser/mambaforge/envs/prd/lib/libz.so  /home/sirfuser/mambaforge/envs/prd/x86_64-conda-linux-gnu/sysroot/usr/lib/libdl.so  /home/sirfuser/mambaforge/envs/prd/x86_64-conda-linux-gnu/sysroot/usr/lib/libm.so  /home/sirfuser/mambaforge/envs/prd/lib/libhdf5_cpp.so  /home/sirfuser/mambaforge/envs/prd/lib/libopenblas.so  -lpthread  -lm  -ldl && :
/data/mambaforge/envs/prd/bin/../lib/gcc/x86_64-conda-linux-gnu/13.3.0/../../../../x86_64-conda-linux-gnu/bin/ld: helpers/CMakeFiles/petsird_generator.dir/petsird_generator.cpp.o: in function `petsird::hdf5::PETSIRDWriter::~PETSIRDWriter()':
petsird_generator.cpp:(.text._ZN7petsird4hdf513PETSIRDWriterD2Ev[_ZN7petsird4hdf513PETSIRDWriterD5Ev]+0xc): undefined reference to `vtable for petsird::hdf5::PETSIRDWriter'

Something subtle about OBJECT libraries in CMake (as petsird_generated is one), I guess. @casperdcl @naegelejd @johnstairs Any ideas?

Originally posted by @KrisThielemans in #161 (comment)