Cluster environments should treat dependencies as system-installed

[nilsvu]

Bug reports:

Some build configurations on clusters emit numerous warnings from headers in our dependencies. We should set up the environments so they treat the dependencies as system-installed to avoid the warnings. This mainly involves replacing CPATH with C_INCLUDE_PATH or CPLUS_INCLUDE_PATH in the environment files.

More information:

• https://gitlab.kitware.com/cmake/cmake/-/issues/19291
• https://gcc.gnu.org/onlinedocs/cpp/Environment-Variables.html

Note that (1) CMake treats include directories from imported targets as "system" by default and (2) even when the CPATH is set the directories should be treated as "system" as of https://gitlab.kitware.com/cmake/cmake/-/merge_requests/3395.

[wthrowe]

To aid others making the change: I believe that our C-compatible dependencies are

• GSL (the GNU one)
• HDF5
• jemalloc
• LIBXSMM
• whatever provides BLAS/LAPACK
• Scotch

and the C++-only ones are

• Charm++
• Blaze
• Boost
• Brigand
• Catch
• libsharp
• yaml-cpp