[Build] Modernize cmake openmp usage (Fix preprocessor and library na…

…me) openMVG#1978

src/CMakeLists.txt

@@ -139,6 +139,7 @@ endif (CXX11_COMPILER)
 if (OpenMVG_USE_OPENMP)
   find_package(OpenMP)
   if (OPENMP_FOUND)
+    register_definitions(-DOPENMVG_USE_OPENMP)
     if(NOT TARGET OpenMP::OpenMP_CXX)
       find_package(Threads REQUIRED)
       add_library(OpenMP::OpenMP_CXX IMPORTED INTERFACE)
@@ -147,8 +148,8 @@ if (OpenMVG_USE_OPENMP)
       # Only works if the same flag is passed to the linker; use CMake 3.9+ otherwise (Intel, AppleClang)
       set_property(TARGET OpenMP::OpenMP_CXX
                    PROPERTY INTERFACE_LINK_LIBRARIES ${OpenMP_CXX_FLAGS} Threads::Threads)
-      list(APPEND OPENMVG_LIBRARY_DEPENDENCIES ${OpenMP_CXX_FLAGS})
     endif()
+    list(APPEND OPENMVG_LIBRARY_DEPENDENCIES OpenMP::OpenMP_CXX)
   endif (OPENMP_FOUND)
 else (OpenMVG_USE_OPENMP)
     option(OpenMVG_USE_OPENMP "Use OpenMP for parallelization" OFF)