fix(build): link SimulcastEncoderAdapter for video encoding support

BuiltinVideoEncoderFactory::CreateVideoEncoder() constructs a
SimulcastEncoderAdapter (builtin_video_encoder_factory.cc:45), but
librtc_simulcast_encoder_adapter.a was never linked into the final
binary. The constructor symbol resolved to 0x0, causing a segfault
on the EncoderQueue when sending video frames through a negotiated
peer connection.

Found via `nm -g wrtc.node | grep "U "` which showed a single
undefined webrtc symbol: SimulcastEncoderAdapterC1.

Author: kevindhanna

CMakeLists.txt

@@ -261,6 +261,7 @@ else()
     ${libwebrtc_binary_dir}/obj/api/video_codecs/libbuiltin_video_encoder_factory.a
     ${libwebrtc_binary_dir}/obj/api/video_codecs/libbuiltin_video_decoder_factory.a
     ${libwebrtc_binary_dir}/obj/media/librtc_internal_video_codecs.a
+    ${libwebrtc_binary_dir}/obj/media/librtc_simulcast_encoder_adapter.a
   )
 endif()
 
@@ -322,6 +323,10 @@ add_library(librtc_internal_video_codecs STATIC IMPORTED)
 add_dependencies(librtc_internal_video_codecs project_libwebrtc)
 set_property(TARGET librtc_internal_video_codecs PROPERTY IMPORTED_LOCATION "${libwebrtc_binary_dir}/obj/media/librtc_internal_video_codecs.a")
 
+add_library(librtc_simulcast_encoder_adapter STATIC IMPORTED)
+add_dependencies(librtc_simulcast_encoder_adapter project_libwebrtc)
+set_property(TARGET librtc_simulcast_encoder_adapter PROPERTY IMPORTED_LOCATION "${libwebrtc_binary_dir}/obj/media/librtc_simulcast_encoder_adapter.a")
+
 set(libc++_include_dir
   "${libwebrtc_source_dir}/src/buildtools/third_party/libc++/trunk/include"
   "${libwebrtc_source_dir}/src/buildtools/third_party/libc++"
@@ -404,6 +409,7 @@ target_link_libraries(${MODULE} PRIVATE
   libbuiltin_video_encoder_factory
   libbuiltin_video_decoder_factory
   librtc_internal_video_codecs
+  librtc_simulcast_encoder_adapter
   ${CMAKE_JS_LIB}
 )
 

scripts/build-webrtc.sh

@@ -6,6 +6,6 @@ set -v
 # We want to use system ninja, _NOT_ depot_tools ninja, actually
 export PATH="${DEPOT_TOOLS}/python-bin:${PATH}:${DEPOT_TOOLS}"
 
-export TARGETS="webrtc libjingle_peerconnection libc++ libc++abi builtin_video_encoder_factory builtin_video_decoder_factory rtc_internal_video_codecs"
+export TARGETS="webrtc libjingle_peerconnection libc++ libc++abi builtin_video_encoder_factory builtin_video_decoder_factory rtc_internal_video_codecs rtc_simulcast_encoder_adapter"
 
 ninja $TARGETS