Auto detect xz compression for input and output

Note that the compression is much slower than with gz, because
the xz compressor cannot yet run multi-threaded. However, xz compression
is typically much better.

Change-Id: Ia8bc7f6238f3c6367fd78ab45d37d2485090ef6f
diff --git a/pom.xml b/pom.xml
index 07b65a5..5603cc8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -224,5 +224,10 @@
             <version>4.12</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.tukaani</groupId>
+            <artifactId>xz</artifactId>
+            <version>1.9</version>
+        </dependency>
     </dependencies>
 </project>
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