make protobuf_MSVC_STATIC_RUNTIME a dependent option to reflect it's use.

cmake/CMakeLists.txt

@@ -20,7 +20,9 @@ else (BUILD_SHARED_LIBS)
   set(protobuf_BUILD_SHARED_LIBS_DEFAULT OFF)
 endif (BUILD_SHARED_LIBS)
 option(protobuf_BUILD_SHARED_LIBS "Build Shared Libraries" ${protobuf_BUILD_SHARED_LIBS_DEFAULT})
-option(protobuf_MSVC_STATIC_RUNTIME "Link static runtime libraries" ON)
+include(CMakeDependentOption)
+cmake_dependent_option(protobuf_MSVC_STATIC_RUNTIME "Link static runtime libraries" ON
+  "NOT protobuf_BUILD_SHARED_LIBS" OFF)
 if (MSVC)
   set(protobuf_WITH_ZLIB_DEFAULT OFF)
 else (MSVC)