Removing $rtc_libyuv_dir and removing useless dependencies on libyuv.

This CL removes the following GN variables: rtc_build_libyuv,
rtc_libyuv_dir (as requested in webrtc:7906).
It also removes some unneeded dependencies on //third_party/libyuv.

WebRTC targets were using public_deps to depend on //third_party/libyuv
and this created a build graph where targets that were depending on
//third_party/libyuv were not declaring the dependency to GN because
they were somehow getting it from another target that was exposing
//third_party/libyuv header files even if it wasn't directly depending
on it.

Bug: webrtc:8605, webrtc:7906
Change-Id: If71f7988fd80421dc2ad887cf94c2ac66366c3fb
Reviewed-on: https://webrtc-review.googlesource.com/32201
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21275}
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index 84c1d9e..2b6d850 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -65,8 +65,6 @@
     "frame_analyzer/video_quality_analysis.h",
   ]
   deps = [
-    "$rtc_libyuv_dir",
-
     # TODO(bugs.webrtc.org/6828): api:optional should be a dependency
     # of rtc_base:rtc_base_approved_generic but that causes a circular
     # dependency. In order to fix the chromium build on MSVC64 (dbg)
@@ -74,6 +72,7 @@
     # symbols it needs.
     "../api:optional",
     "../common_video",
+    "//third_party/libyuv",
   ]
 }
 
@@ -85,7 +84,6 @@
   deps = [
     ":command_line_parser",
     ":video_quality_analysis",
-    "$rtc_libyuv_dir",
     "//build/win:default_exe_manifest",
   ]
 }
@@ -101,7 +99,6 @@
     deps = [
       ":command_line_parser",
       ":video_quality_analysis",
-      "$rtc_libyuv_dir",
       "//build/win:default_exe_manifest",
     ]
   }
@@ -114,7 +111,6 @@
 
     deps = [
       ":video_quality_analysis",
-      "$rtc_libyuv_dir",
     ]
   }
 
@@ -139,9 +135,9 @@
 
     deps = [
       ":command_line_parser",
-      "$rtc_libyuv_dir",
       "../common_video",
       "//build/win:default_exe_manifest",
+      "//third_party/libyuv",
     ]
   }
 
@@ -338,7 +334,6 @@
       ":frame_editing_lib",
       ":reference_less_video_analysis_lib",
       ":video_quality_analysis",
-      "$rtc_libyuv_dir",
       "../common_video:common_video",
       "../rtc_base",
       "../rtc_base:checks",