make VS build link runtime statically

cmake/CMakeLists.txt

@@ -45,6 +45,18 @@ if (MSVC)
     add_definitions(-DPROTOBUF_USE_DLLS)
   endif (BUILD_SHARED_LIBS)
   add_definitions(/wd4244 /wd4267 /wd4018 /wd4355 /wd4800 /wd4251 /wd4996 /wd4146 /wd4305)
+
+  # Link runtime library statically so that MSVCR*.DLL is not required at runtime.
+  # https://msdn.microsoft.com/en-us/library/2kzt1wy3.aspx
+  # This is achieved by replacing msvc option /MD with /MT and /MDd with /MTd
+  # http://www.cmake.org/Wiki/CMake_FAQ#How_can_I_build_my_MSVC_application_with_a_static_runtime.3F
+  foreach(flag_var
+        CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+        CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+    if(${flag_var} MATCHES "/MD")
+      string(REGEX REPLACE "/MD" "/MT" ${flag_var} "${${flag_var}}")
+    endif(${flag_var} MATCHES "/MD")
+  endforeach(flag_var)
 endif (MSVC)
 
 if (MSVC)