Merge pull request #2690 from AndreyMlashkin/make_msvc_runtime_override_optional

add possibility to not override runtime of MSVC
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0600516..2d29062 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -138,7 +138,8 @@
 
 if(WIN32)
     set(CMAKE_DEBUG_POSTFIX "d")
-    if(MSVC)
+    option(OVERRIDE_MSVCCRT "Overrides runtime of MSVC " ON)
+    if(MSVC AND OVERRIDE_MSVCCRT)
         include(ChooseMSVCCRT.cmake)
     endif(MSVC)
     add_definitions(-DGLSLANG_OSINCLUDE_WIN32)