Use elseif(MSVC) to get rid of CMake warning

CMakeLists.txt

@@ -19,7 +19,7 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
 		endif()
 	endif()
 	set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -pthread")
-elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC") # the quotes are needed here, maybe because "MSVC" seems to be a keyword
+elseif(MSVC)
 	if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 19)
 		message(FATAL_ERROR "Visual Studio 2015 or newer is required.")
 	endif()