Merge pull request dftbplus#1345 from bhourahine/NO_OMP_MPI_testers

Only set OMP env for MPI test on enabled build

config.cmake

@@ -94,8 +94,12 @@ option(TEST_WITH_VALGRIND "Whether valgrind should be invoked when testing binar
 # Command line used to launch the test code.
 # The escaped variables (\${VARIABLE}) will be substituted by the corresponding CMake variables.
 if(WITH_MPI)
-  set(TEST_RUNNER_TEMPLATE "env OMP_NUM_THREADS=\${TEST_OMP_THREADS} mpiexec -n \${TEST_MPI_PROCS}"
-    CACHE STRING "How to run the tests")
+  if(WITH_OMP)
+    set(TEST_RUNNER_TEMPLATE "env OMP_NUM_THREADS=\${TEST_OMP_THREADS} mpiexec -n \${TEST_MPI_PROCS}"
+      CACHE STRING "How to run the tests")
+  else()
+    set(TEST_RUNNER_TEMPLATE "mpiexec -n \${TEST_MPI_PROCS}" CACHE STRING "How to run the tests")
+  endif()
 elseif(TEST_WITH_VALGRIND)
   set(VALGRIND_OPTIONS
     "--exit-on-first-error=yes --error-exitcode=1 --leak-check=full --show-leak-kinds=definite,possible --errors-for-leak-kinds=definite,possible"