Deactivate OpenMP in GPU tests

Deactivate OpenMP in GPU tests. OpenMP is only activated in the GPU tests and has proved to be a confounding factor when looking for bugs. In particular issues such as #183 are common with this configuration.

A dedicated OpenMP test should be added once #183 is fixed (before #183 is fixed such a test would fail).

See merge request gysela-developpers/gyselalibxx!427

--------------------------------------------

.gitlab-ci.yml

@@ -63,7 +63,7 @@ cmake_tests_Release_GPU:
     cd build
     cmake -DCMAKE_CXX_COMPILER=${CI_PROJECT_DIR}/vendor/kokkos/bin/nvcc_wrapper \
           -DCMAKE_CXX_FLAGS="-Wall -Wno-sign-compare -Xcudafe --diag_suppress=unsigned_compare_with_zero -Xcudafe --diag_suppress=integer_sign_change" \
-          -DCMAKE_BUILD_TYPE=Release -DDDC_BUILD_TESTS=ON $GENERAL_CMAKE_OPTIONS -DKokkos_ARCH_VOLTA70=ON -DKokkos_ENABLE_SERIAL=ON -DKokkos_ENABLE_OPENMP=ON -DKokkos_ENABLE_CUDA=ON ..
+          -DCMAKE_BUILD_TYPE=Release -DDDC_BUILD_TESTS=ON $GENERAL_CMAKE_OPTIONS -DKokkos_ARCH_VOLTA70=ON -DKokkos_ENABLE_SERIAL=ON -DKokkos_ENABLE_CUDA=ON ..
     make -j 8
     ctest -j 2 --output-on-failure --timeout 5 --output-junit tests.xml -LE ResultsNotTested
     ls ./tests/geometryXVx/landau/fft/growthrate_t0.0to45.0.png