add C++ static link flags for mingw

dev/externals/fastconv/CMakeLists.txt

@@ -4,6 +4,7 @@ if(APPLE)
 else()
   if(MINGW)
     set(CMAKE_C_FLAGS "-O3 -DWIN32 -D_WIN32 -fomit-frame-pointer  -funroll-loops")
+    set(CMAKE_CXX_FLAGS "-O3 -DWIN32 -D_WIN32 -fomit-frame-pointer  -funroll-loops -static-libgcc -static-libstdc++")
   else()
     set(CMAKE_C_FLAGS "-O3 -Wall -Dlinux -Dunix -fomit-frame-pointer -funroll-loops")
   endif()

dev/externals/mctools/CMakeLists.txt

@@ -5,6 +5,7 @@ if(APPLE)
 else()
   if(MINGW)
     set(CMAKE_C_FLAGS "-O3 -DWIN32 -D_WIN32 -fomit-frame-pointer  -funroll-loops")
+    set(CMAKE_CXX_FLAGS "-O3 -DWIN32 -D_WIN32 -fomit-frame-pointer  -funroll-loops -static-libgcc -static-libstdc++")
   else()
     set(CMAKE_C_FLAGS "-O3 -Wall -Dlinux -Dunix -fomit-frame-pointer -funroll-loops")
   endif()