Use output_dir instead of output_name

This is to make second build no-op in mac_asan builder.
e.g. https://ci.chromium.org/p/webrtc/builders/luci.webrtc.try/mac_asan/15219

We can use output_dir to override default_output_dir of executable.
https://gn.googlesource.com/gn/+/master/docs/reference.md#tool-variables


confirm no-op step for this CL does not complain.
https://ci.chromium.org/p/webrtc/builders/luci.webrtc.try/mac_asan/15305

Bug: chromium:914264
Change-Id: Ia1196280064703dcb08e208e91c704cce25a925c
Reviewed-on: https://webrtc-review.googlesource.com/c/114180
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Commit-Queue: Takuto Ikuta <tikuta@google.com>
Cr-Commit-Position: refs/heads/master@{#26013}

modules/audio_processing/test/py_quality_assessment/BUILD.gn

@@ -114,7 +114,7 @@ rtc_executable("fake_polqa") {
     "quality_assessment/fake_polqa.cc",
   ]
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
-  output_name = "py_quality_assessment/quality_assessment/fake_polqa"
+  output_dir = "${root_out_dir}/py_quality_assessment/quality_assessment"
   deps = [
     "../../../..:webrtc_common",
     "../../../../rtc_base:checks",