Add skeleton of perfetto cmdline tool.

Test:
  - ninja -C out/android_x64 perfetto
  - adb shell "stop traced_probes; stop traced; start traced; start traced_probes;"
  - adb push out/android_x64/perfetto /data/local/tmp/ &&  \
      adb push out/android_x64/libtraced_shared.so /data/local/tmp && \
      adb shell "LD_LIBRARY_PATH=/data/local/tmp /data/local/tmp/perfetto -c :test -o /data/local/tmp/trace"

Change-Id: I44d53c5b043df426bcb9e5577fdeaaa387a4eb70
diff --git a/tools/gen_android_bp b/tools/gen_android_bp
index 3c7b96b..48f69ca 100755
--- a/tools/gen_android_bp
+++ b/tools/gen_android_bp
@@ -36,6 +36,7 @@
 # Default targets to translate to the blueprint file.
 default_targets = [
     '//:perfetto_tests',
+    '//:perfetto',
     '//:traced',
     '//:traced_probes',
     '//:libtraced_shared',