Use relative paths in GN files.

webrtc/modules/desktop_capture/BUILD.gn

Index: webrtc/modules/desktop_capture/BUILD.gn
diff --git a/webrtc/modules/desktop_capture/BUILD.gn b/webrtc/modules/desktop_capture/BUILD.gn
index 93ceb752c2e6f0dad56117731e5ef398ec6881f5..f7d6f472da08a0139c4ecc4cf8bdaa49cc1329bb 100644
--- a/webrtc/modules/desktop_capture/BUILD.gn
+++ b/webrtc/modules/desktop_capture/BUILD.gn
@@ -40,7 +40,7 @@ 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 = []
     deps = []
@@ -69,7 +69,7 @@ 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 = [
       "blank_detector_desktop_capturer_wrapper_unittest.cc",