Merge pull request #1483 from akohlmey/cmake-workaround-for-gcc-9

include(CheckIncludeFileCXX)

find_package(OpenMP QUIET)

# TODO: this is a temporary workaround until a better solution is found. AK 2019-05-30

# GNU GCC 9.x uses settings incompatible with our use of 'default(none)' in OpenMP pragmas

# where we assume older GCC semantics. For the time being, we disable OpenMP by default

# for GCC 9.x and beyond. People may manually turn it on, but need to run the script

# src/USER-OMP/hack_openmp_for_pgi_gcc9.sh on all sources to make it compatible with gcc 9.

if ((${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU") AND (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 9.0.0))

  option(BUILD_OMP "Build with OpenMP support" OFF)

else()

  option(BUILD_OMP "Build with OpenMP support" ${OpenMP_FOUND})

endif()

if(BUILD_OMP)

  find_package(OpenMP REQUIRED)

  check_include_file_cxx(omp.h HAVE_OMP_H_INCLUDE)