message: Make rtc_base_approved a rtc_source_set
  A target with only header files should be a source_set.
  Cr-Commit-Position: refs/heads/main@{#36649}
diff: @@ -78,7 +78,7 @@ rtc_source_set("callback_list") {
  # The subset of rtc_base approved for use outside of libjingle.
  # TODO(bugs.webrtc.org/9838): Create small and focused build targets and remove
  # the old concept of rtc_base and rtc_base_approved.
  -rtc_library("rtc_base_approved") {
  +rtc_source_set("rtc_base_approved") {
  visibility = [ "*" ]
  deps = [
  ":atomicops",
  