Mingw 64-bit uses libgcc_s_seh-1 instead of libgcc_s_dw2-1.

CMakeLists.txt

@@ -1062,9 +1062,13 @@ if (WIN32)
   if (NOT LIBSTDC++)
     message(FATAL_ERROR "libstdc++ not found.")
   endif()
-  find_file(LIBDW2 libgcc_s_dw2-1.dll)
+  if ($ENV{MSYSTEM} STREQUAL "MINGW32")
+    find_file(LIBDW2 libgcc_s_dw2-1.dll)
+  else()
+    find_file(LIBDW2 libgcc_s_seh-1.dll)
+  endif()
   if (NOT LIBDW2)
-    message(FATAL_ERROR "libgcc_s_dw2-l not found.")
+    message(FATAL_ERROR "GCC exception library not found.")
   endif()
   set(MINGW_DLLS ${LIBSTDC++} ${LIBDW2})
   install(PROGRAMS ${MINGW_DLLS} DESTINATION ${CMAKE_INSTALL_BINDIR})