Use relative paths in GN files.

webrtc/modules/audio_coding/BUILD.gn

Index: webrtc/modules/audio_coding/BUILD.gn
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index d5b669c0eb381b8b19eaa3d4bf0e4a012cddfcb4..3ea92151e93218da3b313c603fee1d150ba45796 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -1264,7 +1264,7 @@ if (rtc_include_tests) {
     # gets additional generated targets which would require many lines here to
     # cover (which would be confusing to read and hard to maintain).
     if (!is_android && !is_ios) {
-      visibility = [ "//webrtc/modules:modules_tests" ]
+      visibility = [ "..:modules_tests" ]
     }
     sources = [
       "test/ACMTest.h",
@@ -1331,7 +1331,7 @@ if (rtc_include_tests) {
     # gets additional generated targets which would require many lines here to
     # cover (which would be confusing to read and hard to maintain).
     if (!is_android && !is_ios) {
-      visibility = [ "//webrtc:webrtc_perf_tests" ]
+      visibility = [ "../..:webrtc_perf_tests" ]
     }
     sources = [
       "codecs/opus/opus_complexity_unittest.cc",
@@ -1453,7 +1453,7 @@ if (rtc_include_tests) {
   }  # insert_packet_with_timing
 
   audio_decoder_unittests_resources =
-      [ "//resources/audio_coding/testfile32kHz.pcm" ]
+      [ "../../../resources/audio_coding/testfile32kHz.pcm" ]
 
   if (is_ios) {
     bundle_data("audio_decoder_unittests_bundle_data") {
@@ -2061,7 +2061,7 @@ if (rtc_include_tests) {
     # gets additional generated targets which would require many lines here to
     # cover (which would be confusing to read and hard to maintain).
     if (!is_android && !is_ios) {
-      visibility = [ "//webrtc/modules:modules_unittests" ]
+      visibility = [ "..:modules_unittests" ]
     }
     sources = [
       "acm2/acm_receiver_unittest.cc",