remove unused variable

CMakeLists.txt

@@ -376,17 +376,6 @@ if(WIN32)
 endif()
 
 if(MSVC)
-    set(
-      variables
-        CMAKE_C_FLAGS_DEBUG
-        CMAKE_C_FLAGS_MINSIZEREL
-        CMAKE_C_FLAGS_RELEASE
-        CMAKE_C_FLAGS_RELWITHDEBINFO
-        CMAKE_CXX_FLAGS_DEBUG
-        CMAKE_CXX_FLAGS_MINSIZEREL
-        CMAKE_CXX_FLAGS_RELEASE
-        CMAKE_CXX_FLAGS_RELWITHDEBINFO
-    )
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4 /MP")
     if(__BUILD_FOR_R)
         # MSVC does not like this commit: