Update GN files to support build OWT SDK as a shared lib. (#176)

Author: jianjunz

BUILD.gn

@@ -68,15 +68,20 @@ if (!build_with_chromium) {
         "pc:rtc_pc_unittests",
         "pc:slow_peer_connection_unittests",
         "pc:svc_tests",
-        "rtc_tools:rtp_generator",
-        "rtc_tools:video_replay",
         "stats:rtc_stats_unittests",
         "system_wrappers:system_wrappers_unittests",
         "test",
         "video:screenshare_loopback",
         "video:sv_loopback",
         "video:video_loopback",
       ]
+
+      if (!is_component_build) {
+        deps += [
+          "rtc_tools:rtp_generator",
+          "rtc_tools:video_replay",
+        ]
+      }
       if (!is_asan) {
         # Do not build :webrtc_lib_link_test because lld complains on some OS
         # (e.g. when target_os = "mac") when is_asan=true. For more details,
@@ -484,8 +489,8 @@ if (!build_with_chromium) {
   rtc_static_library("webrtc") {
     # Only the root target and the test should depend on this.
     visibility = [
-      ".:default",
       ":webrtc_lib_link_test",
+      ".:default",
     ]
 
     if (build_with_owt) {

webrtc.gni

@@ -14,7 +14,7 @@ import("//build/config/sysroot.gni")
 import("//build_overrides/build.gni")
 import("//build_overrides/ssl/ssl.gni")
 
-if (!build_with_chromium && is_component_build) {
+if (!build_with_chromium && !build_with_owt && is_component_build) {
   print("The Gn argument `is_component_build` is currently " +
         "ignored for WebRTC builds.")
   print("Component builds are supported by Chromium and the argument " +