[tools/perf] Make upload_trace_processor build target visible

BUILD.gn files are read by ninja only if something depends on targets
defined in them. So to make targets in perfetto_binary_roller folder
visible, we provide a special group with a dependency on a target
from it.

Bug: 1050517
Change-Id: I99ca73f11c2a00f70eade250ae9dff93d3c9d3af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2124378Reviewed-by: Wenbin Zhang <wenbinzhang@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Mikhail Khokhlov <khokhlov@google.com>
Cr-Commit-Position: refs/heads/master@{#754594}

tools/perf/BUILD.gn

@@ -93,3 +93,9 @@ group("perf_without_chrome") {
     data_deps += [ "//chrome/android/webapk/shell_apk:maps_go_webapk" ]
   }
 }
+
+# This group makes visible those targets in subdirectories that are not
+# explicitly depended on.
+group("gn_all") {
+  deps = [ "//tools/perf/core/perfetto_binary_roller:upload_trace_processor" ]
+}