blt: linking issue with openmpi on arch linux (blt_mpi_smoke fails to link)

reported by an ascent user, encountered in conduit build.

Is likely a cmake issue, not a blt issue per se.

gcc 9.2.0 on arch linux spack built openmpi-3.1.4 BLT Version: 0.2.5 CMake Version: 3.14.5

[  6%] Linking CXX executable ../../../tests/blt_mpi_smoke
cd BUILD_LOC/spack/var/spack/stage/spack-stage-conduit-master-kxqo2mlz4yzti5ougeq2m2fhlzaa73be/spack-src/spack-build/blt/tests/smoke && BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/cmake-3.14.5-wcfeiamw55g4vwlceklvxyibctne2lgb/bin/cmake -E cmake_link_script CMakeFiles/blt_mpi_smoke.dir/link.txt --verbose=1
/usr/bin/g++      -O2 -g -DNDEBUG  -rdynamic 
-Wl,-rpath -Wl,BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/hwloc-1.11.11-ljswr5og475ralakqrelzykauwnfw3lf/lib 
-Wl,BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib 
-LBUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/hwloc-1.11.11-ljswr5og475ralakqrelzykauwnfw3lf/lib 
-pthread 
CMakeFiles/blt_mpi_smoke.dir/blt_mpi_smoke.cpp.o  
-o ../../../tests/blt_mpi_smoke 
-Wl,-rpath,BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib 
BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib/libmpi.so 
BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib/libmpi_cxx.so 
BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib/libmpi_usempif08.so 
BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib/libmpi_usempi_ignore_tkr.so 
BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib/libmpi_mpifh.so 

Error: ld: BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib: file not recognized: Is a directory Looks like a malformed rpath command, the linker is simply passed a directory:

-Wl,BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib Notice later it is also passed what looks like the expected rpath command:

-Wl,-rpath,BUILD_LOC/spack/opt/spack/linux-arch-sandybridge/gcc-9.2.0/openmpi-3.1.4-7tuxmnjnzj5swmus2shzh3jep2prtzuv/lib