cmake: build ci and and release with static runtime library

(The Visual Studio projects do this as well)

CMakeLists.txt

@@ -4,9 +4,6 @@ if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_CURRENT_BINARY_DIR)
   message(FATAL_ERROR "Prevented in-tree build. Please create a build directory outside of the SDL source code and run \"cmake -S ${CMAKE_SOURCE_DIR} -B .\" from there")
 endif()
 
-# MSVC runtime library flags are selected by an abstraction.
-set(CMAKE_POLICY_DEFAULT_CMP0091 NEW)
-
 # See docs/release_checklist.md
 project(SDL3 LANGUAGES C VERSION "3.1.2")