Add pw_bloat module

This change adds a size reporting module named pw_bloat. The module
uses Bloaty McBloatface to generate size report cards for binaries. It
provides a GN template which defines an action to perform a size diff
on a group of binary targets.

Example output:

                       simple_bloat
                       ────────────
┌────────────────┬──────────────┬────────┬───────┬───────┐
│      Label     │    Segment   │ Before │ Delta │ After │
├════════════════┼══════════════┼════════┼═══════┼═══════┤
│     Add a loop │ EXAMPLE CODE │    429 │   +32 │   461 │
│                │ EXAMPLE  RAM │    576 │    +8 │   584 │
├────────────────┼──────────────┼────────┼───────┼───────┤
│ Add a function │ EXAMPLE CODE │    429 │   +16 │   445 │
│                │ EXAMPLE  RAM │    576 │    +8 │   584 │
└────────────────┴──────────────┴────────┴───────┴───────┘

Change-Id: I14b3d383ec450bc6d017bf5d0111e266b0a3c368
diff --git a/targets/host/linux.bloaty b/targets/host/linux.bloaty
new file mode 100644
index 0000000..ff9dd2e
--- /dev/null
+++ b/targets/host/linux.bloaty
@@ -0,0 +1,27 @@
+# Copyright 2019 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+custom_data_source: {
+  name: "segment_names"
+  base_data_source: "segments"
+
+  rewrite: {
+    pattern: "LOAD #3"
+    replacement: "CODE"
+  }
+  rewrite: {
+    pattern: "LOAD #5"
+    replacement: "RAM"
+  }
+}