build: switch source archive to xz compression

Change-Id: I8ec1968161aa6c85bf9ba7dd7859e81b160fabfb
diff --git a/wscript b/wscript
index 2b0f21d..99283ed 100644
--- a/wscript
+++ b/wscript
@@ -144,7 +144,9 @@
         Logs.warn('%s is not writable (%s)' % (versionFile, e.strerror))
 
 def dist(ctx):
+    ctx.algo = 'tar.xz'
     version(ctx)
 
 def distcheck(ctx):
+    ctx.algo = 'tar.xz'
     version(ctx)