CMake: Modifiy CMAKE_CXX_FLAGS* after enable_language(CXX)

Brought to the surface by link errors in AppVeyor:
error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MT_StaticRelease' doesn't match value 'MD_DynamicRelease'

CMakeLists.txt

@@ -76,20 +76,17 @@ if(URIPARSER_BUILD_TOOLS AND NOT URIPARSER_BUILD_CHAR)
     message(SEND_ERROR "URIPARSER_BUILD_TOOLS=ON requires URIPARSER_BUILD_CHAR=ON.")
 endif()
 
+macro(uriparser_apply_msvc_runtime_to ref)
+    string(REGEX REPLACE "/M[DT]d?" ${URIPARSER_MSVC_RUNTIME} ${ref} "${${ref}}")
+endmacro()
+
 if(MSVC AND URIPARSER_MSVC_RUNTIME)
-    set(_refs
-        CMAKE_CXX_FLAGS
-        CMAKE_CXX_FLAGS_DEBUG
-        CMAKE_CXX_FLAGS_RELEASE
-        CMAKE_C_FLAGS
-        CMAKE_C_FLAGS_DEBUG
-        CMAKE_C_FLAGS_RELEASE
-    )
-    foreach(_ref ${_refs})
-        string(REGEX REPLACE "/M[DT]d?" ${URIPARSER_MSVC_RUNTIME} ${_ref} "${${_ref}}")
-    endforeach()
+    uriparser_apply_msvc_runtime_to(CMAKE_C_FLAGS)
+    uriparser_apply_msvc_runtime_to(CMAKE_C_FLAGS_DEBUG)
+    uriparser_apply_msvc_runtime_to(CMAKE_C_FLAGS_RELEASE)
 endif()
 
+
 #
 # Compiler checks
 #
@@ -246,6 +243,12 @@ endif()
 if(URIPARSER_BUILD_TESTS)
     enable_language(CXX)
 
+    if(MSVC AND URIPARSER_MSVC_RUNTIME)
+        uriparser_apply_msvc_runtime_to(CMAKE_CXX_FLAGS)
+        uriparser_apply_msvc_runtime_to(CMAKE_CXX_FLAGS_DEBUG)
+        uriparser_apply_msvc_runtime_to(CMAKE_CXX_FLAGS_RELEASE)
+    endif()
+
     enable_testing()
 
     find_package(GTest 1.8.0 REQUIRED)