Update Checkstyle config to ignore generated sources

Change-Id: Iaead8d846cb1bd2e9240bc52ee0feabdfd3ffddf

tools/checkstyle.xml

diff --git a/tools/checkstyle.xml b/tools/checkstyle.xml
index fc94144..1bb40f7 100644
--- a/tools/checkstyle.xml
+++ b/tools/checkstyle.xml
@@ -104,4 +104,7 @@
     <property name="checkFormat" value="$1"/>
     <property name="influenceFormat" value="$2"/>
   </module>
+  <module name="SuppressionFilter">
+    <property name="file" value="${samedir}/checkstyle_suppressions.xml"/>
+  </module>
 </module>

tools/checkstyle_suppressions.xml

diff --git a/tools/checkstyle_suppressions.xml b/tools/checkstyle_suppressions.xml
new file mode 100644
index 0000000..5f5d9ee
--- /dev/null
+++ b/tools/checkstyle_suppressions.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0"?>
+
+<!DOCTYPE suppressions PUBLIC
+  "-//Puppy Crawl//DTD Suppressions 1.1//EN"
+  "http://www.puppycrawl.com/dtds/suppressions_1_1.dtd">
+<suppressions>
+  <suppress files="[/\\].apt_generated[/\\]" checks=".*"/>
+</suppressions>