Rectify comment about 'build_with_chromium'.

Bug: webrtc:9988
Change-Id: I0cc7e0c9da0ff969d6269086c9df8f6725536da5
No-Try: True
Reviewed-on: https://webrtc-review.googlesource.com/c/110862
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25631}
diff --git a/build_overrides/build.gni b/build_overrides/build.gni
index 81cb3e7..5d8af6d 100644
--- a/build_overrides/build.gni
+++ b/build_overrides/build.gni
@@ -12,8 +12,8 @@
 # Some non-Chromium builds don't use Chromium's third_party/binutils.
 linux_use_bundled_binutils_override = true
 
-# Variable that can be used to support multiple build scenarios, like having
-# Chromium specific targets in a client project's GN file etc.
+# Don't set this variable to true when building stadalone WebRTC, it is
+# only needed to support both WebRTC standalone and Chromium builds.
 build_with_chromium = false
 
 # Use our own suppressions files.