GN: Change rtc_source_set targets --> rtc_static_library

webrtc/BUILD.gn

Index: webrtc/BUILD.gn
diff --git a/webrtc/BUILD.gn b/webrtc/BUILD.gn
index 47b757a237fafa0c8de3bdf438f76edc965af542..d4308e12c5c809da5e727770d03d82fef0b716ca 100644
--- a/webrtc/BUILD.gn
+++ b/webrtc/BUILD.gn
@@ -287,7 +287,7 @@ if (!is_ios || !build_with_chromium) {
   }
 }
 
-rtc_source_set("webrtc_common") {
+rtc_static_library("webrtc_common") {
   sources = [
     "common_types.cc",
     "common_types.h",
@@ -313,7 +313,7 @@ if (rtc_enable_protobuf) {
   }
 }
 
-rtc_source_set("rtc_event_log") {
+rtc_static_library("rtc_event_log") {
   sources = [
     "call/rtc_event_log.cc",
     "call/rtc_event_log.h",
@@ -340,7 +340,7 @@ rtc_source_set("rtc_event_log") {
 }
 
 if (rtc_enable_protobuf) {
-  rtc_source_set("rtc_event_log_parser") {
+  rtc_static_library("rtc_event_log_parser") {
     sources = [
       "call/rtc_event_log_parser.cc",
       "call/rtc_event_log_parser.h",