Add a SWIFT_STDLIB_STABLE_ABI flag to be able to build the stdlib without -enable-library-evolution (#33443)

utils/build-script-impl

@@ -197,6 +197,7 @@ KNOWN_SETTINGS=(
     swift-runtime-macho-no-dyld                   "0"               "whether to build stdlib assuming the runtime environment does not support dynamic modules"
     swift-stdlib-single-threaded-runtime          "0"               "whether to build stdlib as a single-threaded runtime only"
     swift-stdlib-os-versioning                    "1"               "whether to build stdlib with availability based on OS versions (Darwin only)"
+    swift-stdlib-stable-abi                       ""                "should stdlib be built with stable ABI, if not set defaults to true on Darwin, false otherwise"
 
     ## FREESTANDING Stdlib Options
     swift-freestanding-sdk                      ""                "which SDK to use when building the FREESTANDING stdlib"
@@ -1872,6 +1873,13 @@ for host in "${ALL_HOSTS[@]}"; do
                     )
                 fi
 
+                if [[ "${SWIFT_STDLIB_STABLE_ABI}" ]] ; then
+                    cmake_options=(
+                        "${cmake_options[@]}"
+                        -DSWIFT_STDLIB_STABLE_ABI:BOOL=$(true_false "${SWIFT_STDLIB_STABLE_ABI}")
+                    )
+                fi
+
                 if [ "${SWIFT_INSTALL_COMPONENTS}" ] ; then
                     cmake_options=(
                         "${cmake_options[@]}"