[CMake] StandaloneOverlay: set components before including apinotes/ (#22601)

Otherwise, we'll think we don't need to install the API notes.

No test because this configuration isn't (yet) tested publicly
anywhere, but it is being tested within Apple.

(cherry picked from commit bc35b34)

Author: jrose-apple

apinotes/CMakeLists.txt

@@ -28,6 +28,10 @@ add_custom_target("copy_apinotes"
     COMMENT "Copying API notes to ${output_dir}"
     SOURCES "${sources}")
 
+# This is treated as an OPTIONAL target because if we don't build the SDK
+# overlay, the files will be missing anyway. It also allows us to build
+# single overlays without installing the API notes.
 swift_install_in_component(sdk-overlay
-    FILES ${sources}
-    DESTINATION "lib/swift/apinotes")
+    DIRECTORY "${output_dir}"
+    DESTINATION "lib/swift/"
+    OPTIONAL)

cmake/modules/StandaloneOverlay.cmake

@@ -59,14 +59,14 @@ precondition(SWIFT_DEST_ROOT)
 precondition(SWIFT_HOST_VARIANT_SDK)
 precondition(TOOLCHAIN_DIR)
 
+# Without this line, installing components is broken. This needs refactoring.
+swift_configure_components()
+
 # Some overlays include the runtime's headers,
 # and some of those headers are generated at build time.
 add_subdirectory("${SWIFT_SOURCE_DIR}/include" "${SWIFT_SOURCE_DIR}/include")
 add_subdirectory("${SWIFT_SOURCE_DIR}/apinotes" "${SWIFT_SOURCE_DIR}/apinotes")
 
-# Without this line, installing components is broken. This needs refactoring.
-swift_configure_components()
-
 precondition(unknown_sdks NEGATE MESSAGE "Unknown SDKs: ${unknown_sdks}")
 precondition(SWIFT_CONFIGURED_SDKS MESSAGE "No SDKs selected.")
 precondition(SWIFT_HOST_VARIANT_SDK MESSAGE "No SDK for host tools.")