libmetrics: add pkg-config file

BUG=chromium:366984
TEST=`FEATURES=test emerge-$BOARD platform2` and verify libmetrics-242728.pc is created.

Change-Id: I3cd79e7421a5f666a4bf2551c87086f779078771
Reviewed-on: https://chromium-review.googlesource.com/196974
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>

metrics/libmetrics.pc.in

@@ -0,0 +1,7 @@
+bslot=@BSLOT@
+
+Name: libmetrics
+Description: Chrome OS metrics library
+Version: ${bslot}
+Requires.private: libchrome-${bslot}
+Libs: -lmetrics-${bslot}

metrics/platform2_preinstall.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+set -e
+
+OUT=$1
+shift
+for v; do
+  sed -e "s/@BSLOT@/${v}/g" libmetrics.pc.in > "${OUT}/lib/libmetrics-${v}.pc"
+done