Expand is_linux to is_linux || is_chromeos.

Currently is_linux is set to true on Chrome OS build,
but it is planned to be set false. This CL is the preparation
to keep the compatibility.

Bug: chromium:1110266
Test: Build locally.
Change-Id: Ic79a202b0b3baeff157955cd03a07556bfb958a8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/183860
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#32073}

audio/BUILD.gn

@@ -254,7 +254,7 @@ if (rtc_include_tests) {
         data += [ "${root_out_dir}/low_bandwidth_audio_test" ]
       }
 
-      if (is_linux || is_android) {
+      if (is_linux || is_chromeos || is_android) {
         data += [
           "../tools_webrtc/audio_quality/linux/PolqaOem64",
           "../tools_webrtc/audio_quality/linux/pesq",