FindMPI: Link flags incorrectly de-duplicated by CMake 3.15.0
The change in !3449 (merged) causes de-duplication of flags provided by MPI, which is incorrect in cases like -Wl,-rpath -Wl,/some/path -Wl,-rpath -Wl,/other/path
. See spack issue 12120 and !3449 (comment 600811).