Replace accidental usages of source_set with rtc_source_set

Bug: None
Change-Id: I80c5ad9e1e9942eb51ace014cd7b9127959d601b
Reviewed-on: https://webrtc-review.googlesource.com/89061
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24004}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 18d6897..982d5c4 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -60,7 +60,7 @@
   }
 }
 
-source_set("protobuf_utils") {
+rtc_source_set("protobuf_utils") {
   visibility = [ "*" ]
   sources = [
     "protobuf_utils.h",
@@ -72,7 +72,7 @@
   }
 }
 
-source_set("compile_assert_c") {
+rtc_source_set("compile_assert_c") {
   sources = [
     "compile_assert_c.h",
   ]