Linux: add system audio capture for desktop sharing

Author: paterkleomenis

CMakeLists.txt

@@ -22,6 +22,8 @@ PRIVATE
     webrtc/webrtc_device_resolver.h
     webrtc/webrtc_environment.cpp
     webrtc/webrtc_environment.h
+    webrtc/webrtc_system_audio_capture.cpp
+    webrtc/webrtc_system_audio_capture.h
     webrtc/webrtc_video_track.cpp
     webrtc/webrtc_video_track.h
 
@@ -34,6 +36,12 @@ PRIVATE
 
     webrtc/platform/linux/webrtc_environment_linux.cpp
     webrtc/platform/linux/webrtc_environment_linux.h
+    webrtc/platform/linux/webrtc_loopback_adm_linux.cpp
+    webrtc/platform/linux/webrtc_loopback_adm_linux.h
+    webrtc/platform/linux/webrtc_loopback_capture_linux.cpp
+    webrtc/platform/linux/webrtc_loopback_capture_linux.h
+    webrtc/platform/linux/webrtc_system_audio_capture_linux.cpp
+    webrtc/platform/linux/webrtc_system_audio_capture_linux.h
     webrtc/platform/mac/webrtc_environment_mac.h
     webrtc/platform/mac/webrtc_environment_mac.mm
     webrtc/platform/win/webrtc_environment_win.cpp
@@ -55,6 +63,11 @@ elseif (APPLE)
     PRIVATE
         WEBRTC_MAC
     )
+elseif (LINUX)
+    target_compile_definitions(lib_webrtc
+    PRIVATE
+        WEBRTC_LINUX
+    )
 endif()
 
 target_include_directories(lib_webrtc