trace_processor: implement first android mem metric!

We fill the LMK field for now: more metrics will be filled in following
CLs.

Context: go/perfetto-metrics
Bug: 129747127
Change-Id: If3d7de375e16bbfd15a8b19bda05d3162ae30308
diff --git a/BUILD.extras b/BUILD.extras
index a1ca2c3..1139c44 100644
--- a/BUILD.extras
+++ b/BUILD.extras
@@ -11,3 +11,10 @@
         ":trace_to_text",
     ],
 )
+
+py_binary(
+    name = "gen_merged_sql_metrics_py"
+    srcs = [
+      "tools/gen_merged_sql_metrics"
+    ]
+)