minijail: Create a pkgconfig file for libminijail.

This allows us to change the import path of libminijail.h easily.

BUG=None
TEST=`emerge-gizmo apmanager attestation cromo cros-disks debugd
libchromeos lorgnette minijail tpm_manager trunks webserver` works.

CQ-DEPEND=CL:293580

Change-Id: I4b44174ae115a93fb9d4299ca24002f9ad37ba6c
Reviewed-on: https://chromium-review.googlesource.com/293483
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
Trybot-Ready: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
diff --git a/libminijail.pc.in b/libminijail.pc.in
new file mode 100644
index 0000000..29f7c77
--- /dev/null
+++ b/libminijail.pc.in
@@ -0,0 +1,8 @@
+bslot=@BSLOT@
+include_dir=@INCLUDE_DIR@
+
+Name: libminijail
+Description: Minijail shared library.
+Version: ${bslot}
+CFlags: -I${include_dir}
+Libs: -lminijail
diff --git a/platform2_preinstall.sh b/platform2_preinstall.sh
new file mode 100755
index 0000000..7d19d99
--- /dev/null
+++ b/platform2_preinstall.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# Copyright 2015 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
+
+v=$1
+include_dir=$2
+
+sed \
+  -e "s/@BSLOT@/${v}/g" \
+  -e "s:@INCLUDE_DIR@:${include_dir}:g" \
+  "libminijail.pc.in" > "libminijail.pc"