[OpenMP] Only enable version script if supported

[tianshilei1992]

Summary

The linker flag --version-script may not be supported by all linkers, such as
macOS's linker. libomp is already capable of detecting whether the linker supports
it and append the linker flag accordingly. Since currently we assume libomptarget
only works on Linux, we don't do the check accordingly. This patch simply adds
the check before adding it to linker flag. This will be the first patch to make
OpenMP target offloading work on macOS. Note that CMake files in plugins are
not touched before they are going to be removed pretty soon anyway.

[tianshilei1992]

openmp/libomptarget/src/CMakeLists.txt

33–34

Actually we can remove it now

[jhuber6]

This should be fine for targets that don't support it, thanks.

openmp/libomptarget/plugins-nextgen/CMakeLists.txt

add_llvm_library("omptarget.rtl.${tmachine_libname}.nextgen"
 
         LINK_LIBS
         PRIVATE
         elf_common
         MemoryManager
         PluginInterface
         ${LIBOMPTARGET_DEP_LIBFFI_LIBRARIES}
         ${OPENMP_PTHREAD_LIB}
-        "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports"
 
       NO_INSTALL_RPATH
     )
 
+    if (LIBOMP_HAVE_VERSION_SCRIPT_FLAG)
+      target_link_libraries("omptarget.rtl.${tmachine_libname}.nextgen" PRIVATE
+        "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports")
+    endif()
+
     # Install plugin under the lib destination folder.
     install(TARGETS "omptarget.rtl.${tmachine_libname}.nextgen"
       LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
     set_target_properties("omptarget.rtl.${tmachine_libname}.nextgen" PROPERTIES
       INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
       CXX_VISIBILITY_PRESET protected)
 
     target_include_directories( "omptarget.rtl.${tmachine_libname}.nextgen" PRIVATE

openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt

add_llvm_library(omptarget.rtl.amdgpu.nextgen SHARED
 
   LINK_LIBS
   PRIVATE
   elf_common
   MemoryManager
   PluginInterface
   ${LIBOMPTARGET_DEP_LIBRARIES}
   ${OPENMP_PTHREAD_LIB}
-  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports"
   ${LDFLAGS_UNDEFINED}
 
   NO_INSTALL_RPATH
 )
 
+if (LIBOMP_HAVE_VERSION_SCRIPT_FLAG)
+  target_link_libraries(omptarget.rtl.amdgpu.nextgen PRIVATE
+    "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports")
+endif()
+
 target_include_directories(
   omptarget.rtl.amdgpu.nextgen
   PRIVATE
   ${LIBOMPTARGET_INCLUDE_DIR}
   ${CMAKE_CURRENT_SOURCE_DIR}/utils
 )
 
 
 # Install plugin under the lib destination folder.
 install(TARGETS omptarget.rtl.amdgpu.nextgen LIBRARY DESTINATION "${OPENMP_INSTALL_LIBDIR}")
 set_target_properties(omptarget.rtl.amdgpu.nextgen PROPERTIES
   INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/.."
   CXX_VISIBILITY_PRESET protected)

openmp/libomptarget/plugins-nextgen/cuda/CMakeLists.txt

add_llvm_library(omptarget.rtl.cuda.nextgen SHARED
   Support
   Object
 
   LINK_LIBS PRIVATE
   elf_common
   MemoryManager
   PluginInterface
   ${OPENMP_PTHREAD_LIB}
-  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports,-z,defs"
 
   NO_INSTALL_RPATH
 )
 
+if (LIBOMP_HAVE_VERSION_SCRIPT_FLAG)
+  target_link_libraries(omptarget.rtl.cuda.nextgen PRIVATE
+  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/../exports,-z,defs")
+endif()
+
+
 if(LIBOMPTARGET_DEP_CUDA_FOUND AND NOT LIBOMPTARGET_FORCE_DLOPEN_LIBCUDA)
   libomptarget_say("Building CUDA plugin linked against libcuda")
   target_link_libraries(omptarget.rtl.cuda.nextgen PRIVATE CUDA::cuda_driver)
 else()
   libomptarget_say("Building CUDA plugin for dlopened libcuda")
   target_include_directories(omptarget.rtl.cuda.nextgen PRIVATE ../../plugins/cuda/dynamic_cuda)
   target_sources(omptarget.rtl.cuda.nextgen PRIVATE ../../plugins/cuda/dynamic_cuda/cuda.cpp)
 endif()

openmp/libomptarget/src/CMakeLists.txt

add_llvm_library(omptarget
   LegacyAPI.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LIBOMPTARGET_INCLUDE_DIR}
 
   LINK_COMPONENTS
   Support
   Object
 
-  LINK_LIBS
-  PRIVATE
-  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports"
   NO_INSTALL_RPATH
 )
 target_include_directories(omptarget PRIVATE ${LIBOMPTARGET_INCLUDE_DIR})
 
+if (LIBOMP_HAVE_VERSION_SCRIPT_FLAG)
+  target_link_libraries(omptarget PRIVATE
+    "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports")
+endif()
+
 # libomptarget.so needs to be aware of where the plugins live as they
 # are now separated in the build directory.
 set_target_properties(omptarget PROPERTIES INSTALL_RPATH "$ORIGIN" BUILD_RPATH "$ORIGIN:${CMAKE_CURRENT_BINARY_DIR}/..")
 install(TARGETS omptarget LIBRARY COMPONENT omptarget DESTINATION "${OPENMP_INSTALL_LIBDIR}")