Move over to ABSL logging and flags.

Removes gperftools too since that wants gflags.

Here come the fireworks.

Change-Id: I79cb7bcf60f1047fbfa28bfffc21a0fd692e4b1c
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/events/glib_main_loop.h b/aos/events/glib_main_loop.h
index 080bc57..782043b 100644
--- a/aos/events/glib_main_loop.h
+++ b/aos/events/glib_main_loop.h
@@ -247,7 +247,7 @@
       signal_handler_id_(g_signal_connect(
           instance, detailed_signal,
           G_CALLBACK(&GlibSignalCallback::InvokeSignal), user_data())) {
-  CHECK_GT(signal_handler_id_, 0);
+  CHECK_GT(signal_handler_id_, 0u);
   VLOG(1) << this << " connected glib signal with " << user_data() << " as "
           << signal_handler_id_ << " on " << instance << ": "
           << detailed_signal;