GN: Change rtc_source_set targets --> rtc_static_library

This changes most non-test related rtc_source_set targets to be
rtc_static_library instead. Targets without any .cc files are excluded.
This should bring back the build behavior we used to have with GYP
(i.e. same symbols exported in the libjingle_peerconnection.a file, which
are used by some downstream projects).

After doing an Android build with these changes:
$ nm --defined-only -g -C out/Release/lib.unstripped/libjingle_peerconnection_so.so | grep -i createpeerconnectionf
00077c51 T Java_org_webrtc_PeerConnectionFactory_nativeCreatePeerConnectionFactory
$ nm --defined-only -g -C out/Release/obj/webrtc/api/libjingle_peerconnection.a | grep -i createpeerconnectionf
00000001 T webrtc::CreatePeerConnectionFactory(rtc::Thread*, rtc::Thread*, rtc::Thread*, webrtc::AudioDeviceModule*, cricket::WebRtcVideoEncoderFactory*, cricket::WebRtcVideoDecoderFactory*)
00000001 T webrtc::CreatePeerConnectionFactory()

See https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/cookbook.md#Note-on-static-libraries
for more details on this.

NOTICE: This should be further cleaned up in the future, to reduce
binary bloat and unnecessary linking time. Right now it's more
important to restore the desired build output though.

BUG=webrtc:6410, chromium:630755

Review-Url: https://codereview.webrtc.org/2361623004
Cr-Commit-Position: refs/heads/master@{#14364}
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index a69206e..fceff9b 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -39,7 +39,7 @@
                       "../../system_wrappers",
                     ]
 
-rtc_source_set("audio_decoder_factory_interface") {
+rtc_static_library("audio_decoder_factory_interface") {
   sources = [
     "codecs/audio_decoder_factory.h",
     "codecs/audio_format.cc",
@@ -50,7 +50,7 @@
   ]
 }
 
-rtc_source_set("builtin_audio_decoder_factory") {
+rtc_static_library("builtin_audio_decoder_factory") {
   sources = [
     "codecs/builtin_audio_decoder_factory.cc",
     "codecs/builtin_audio_decoder_factory.h",
@@ -62,7 +62,7 @@
   defines = audio_codec_defines
 }
 
-rtc_source_set("rent_a_codec") {
+rtc_static_library("rent_a_codec") {
   sources = [
     "acm2/acm_codec_database.cc",
     "acm2/acm_codec_database.h",
@@ -80,7 +80,7 @@
   ]
 }
 
-rtc_source_set("audio_coding") {
+rtc_static_library("audio_coding") {
   sources = [
     "acm2/acm_common_defs.h",
     "acm2/acm_receiver.cc",
@@ -124,7 +124,7 @@
   defines = audio_coding_defines
 }
 
-rtc_source_set("audio_decoder_interface") {
+rtc_static_library("audio_decoder_interface") {
   sources = [
     "codecs/audio_decoder.cc",
     "codecs/audio_decoder.h",
@@ -137,7 +137,7 @@
   ]
 }
 
-rtc_source_set("audio_encoder_interface") {
+rtc_static_library("audio_encoder_interface") {
   sources = [
     "codecs/audio_encoder.cc",
     "codecs/audio_encoder.h",
@@ -155,7 +155,7 @@
   ]
 }
 
-rtc_source_set("cng") {
+rtc_static_library("cng") {
   sources = [
     "codecs/cng/audio_encoder_cng.cc",
     "codecs/cng/audio_encoder_cng.h",
@@ -175,7 +175,7 @@
   include_dirs = [ "codecs/red" ]
 }
 
-rtc_source_set("red") {
+rtc_static_library("red") {
   sources = [
     "codecs/red/audio_encoder_copy_red.cc",
     "codecs/red/audio_encoder_copy_red.h",
@@ -196,7 +196,7 @@
   ]
 }
 
-rtc_source_set("g711") {
+rtc_static_library("g711") {
   sources = [
     "codecs/g711/audio_decoder_pcm.cc",
     "codecs/g711/audio_decoder_pcm.h",
@@ -223,7 +223,7 @@
   ]
 }
 
-rtc_source_set("g722") {
+rtc_static_library("g722") {
   sources = [
     "codecs/g722/audio_decoder_g722.cc",
     "codecs/g722/audio_decoder_g722.h",
@@ -251,7 +251,7 @@
   ]
 }
 
-rtc_source_set("ilbc") {
+rtc_static_library("ilbc") {
   sources = [
     "codecs/ilbc/abs_quant.c",
     "codecs/ilbc/abs_quant.h",
@@ -408,7 +408,7 @@
   ]
 }
 
-rtc_source_set("isac_common") {
+rtc_static_library("isac_common") {
   sources = [
     "codecs/isac/audio_encoder_isac_t.h",
     "codecs/isac/audio_encoder_isac_t_impl.h",
@@ -424,7 +424,7 @@
   ]
 }
 
-rtc_source_set("isac") {
+rtc_static_library("isac") {
   sources = [
     "codecs/isac/main/include/audio_decoder_isac.h",
     "codecs/isac/main/include/audio_encoder_isac.h",
@@ -505,7 +505,7 @@
   ]
 }
 
-rtc_source_set("isac_fix") {
+rtc_static_library("isac_fix") {
   sources = [
     "codecs/isac/fix/include/audio_decoder_isacfix.h",
     "codecs/isac/fix/include/audio_encoder_isacfix.h",
@@ -608,7 +608,7 @@
 }
 
 if (rtc_build_with_neon) {
-  rtc_source_set("isac_neon") {
+  rtc_static_library("isac_neon") {
     sources = [
       "codecs/isac/fix/source/entropy_coding_neon.c",
       "codecs/isac/fix/source/filterbanks_neon.c",
@@ -647,7 +647,7 @@
   ]
 }
 
-rtc_source_set("pcm16b") {
+rtc_static_library("pcm16b") {
   sources = [
     "codecs/pcm16b/audio_decoder_pcm16b.cc",
     "codecs/pcm16b/audio_decoder_pcm16b.h",
@@ -670,7 +670,7 @@
   include_dirs = [ "../../.." ]
 }
 
-rtc_source_set("webrtc_opus") {
+rtc_static_library("webrtc_opus") {
   sources = [
     "codecs/opus/audio_decoder_opus.cc",
     "codecs/opus/audio_decoder_opus.h",
@@ -749,7 +749,7 @@
   ]
 }
 
-rtc_source_set("neteq") {
+rtc_static_library("neteq") {
   sources = [
     "neteq/accelerate.cc",
     "neteq/accelerate.h",
@@ -1002,7 +1002,7 @@
       proto_out_dir = "webrtc/audio_coding/neteq"
     }
 
-    rtc_source_set("rtc_event_log_source") {
+    rtc_static_library("rtc_event_log_source") {
       testonly = true
       sources = [
         "neteq/tools/rtc_event_log_source.cc",