Fix OpenMP link error on MinGW.

CMakeLists.txt

@@ -157,10 +157,17 @@ if( CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang" )
     endif()
 
     find_package( OpenMP QUIET )
+
     if( OPENMP_FOUND )
         set( CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${OpenMP_C_FLAGS}" )
         set( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}" )
         add_definitions( -DUSE_OPENMP )
+
+        # MinGW does not include the OpenMP link library and FindOpenMP.cmake does not
+        # set it either.  Not sure this is the most elegant solution but it works.
+        if( MINGW )
+            set( OPENMP_LIBRARIES gomp )
+        endif()
     endif()
 
     if( MINGW )

cvpcb/CMakeLists.txt

@@ -116,6 +116,7 @@ if( USE_KIWAY_DLLS )
         ${GLEW_LIBRARIES}
         ${CAIRO_LIBRARIES}
         ${PIXMAN_LIBRARY}
+        ${OPENMP_LIBRARIES}
         )
 
     # Only for win32 cross compilation using MXE

pcbnew/CMakeLists.txt

@@ -536,6 +536,7 @@ if( USE_KIWAY_DLLS )
         OUTPUT_NAME     pcbnew
         PREFIX          ${KIFACE_PREFIX}
         SUFFIX          ${KIFACE_SUFFIX}
+        COMPILE_FLAGS   ${OpenMP_CXX_FLAGS}
         )
     target_link_libraries( pcbnew_kiface
         3d-viewer
@@ -557,6 +558,7 @@ if( USE_KIWAY_DLLS )
         ${PIXMAN_LIBRARY}
         ${Boost_LIBRARIES}      # must follow GITHUB
         ${PCBNEW_EXTRA_LIBS}    # -lrt must follow Boost
+        ${OPENMP_LIBRARIES}
         )
     set_source_files_properties( pcbnew.cpp PROPERTIES
         # The KIFACE is in pcbnew.cpp, export it: