Update the LLVM version in the Windows CMake script

My CI on Windows has been failing for various reasons for the past few
months and I didn't notice this when updating llvm-tutor to LLVM 11.

Support for Windows remains "experimental".

HelloWorld/CMakeLists.txt_for_windows

@@ -4,7 +4,7 @@
 # required for Windows only.
 #===============================================================================
 
-cmake_minimum_required(VERSION 3.4.3)
+cmake_minimum_required(VERSION 3.13.4)
 project(llvm-tutor-hello-world)
 
 #===============================================================================
@@ -17,7 +17,7 @@ set(LT_LLVM_INSTALL_DIR "" CACHE PATH "LLVM installation directory")
 # find_package can locate it)
 list(APPEND CMAKE_PREFIX_PATH "${LT_LLVM_INSTALL_DIR}/lib/cmake/llvm/")
 
-find_package(LLVM 10.0.0 REQUIRED CONFIG)
+find_package(LLVM 11.0.0 REQUIRED CONFIG)
 
 # HelloWorld includes headers from LLVM - update the include paths accordingly
 include_directories(${LLVM_INCLUDE_DIRS})