Issues with using target aliases

[gkaf89]

Target aliases such as MPI::MPI_C populated by the find_package command for MPI can introduce unwanted artifacts such as RUNPATH entries in the final build.

I am building ScaLAPACK in a HPC systems where MPI libraries are loaded with modules. For some MPI modules, CMake inserts into the linker flags, MPI_<language>_LINK_FLAGS, run path entries -Wl,-rpath -Wl,<path>. These entries are not removed from the RUNPATH of the installed executable. I have more details in the Stack Overflow issue "Use of MPI::MPI_C alias".

Since the find module for MPI offers no control on how it sets up the alias targets it exposes, it seems that the only solution is to use exposed variables, such as MPI_C_INCLUDE_DIRS and MPI_C_LIBRARIES to explicitly set up all the required target properties.

Aliases are a convenient abstraction, but without a well designed API using them across projects causes issues. Would it make sense to replace aliases in the CMake scripts with explicit variables?

P.S.

I know that this is not the official repository for ScaLAPACK, but

1. this repo has more up-to-date CMake files that can filter down stream, and
2. the issue may affect other projects using MPI such as MUMPS.