Change to maximum compression level when using lzma

The deploy image is getting larger and larger, by specifying a higher
compression level, usualy we can save a couple of MB. Smaller image
has higher performance when deploying nodes with PXE.

This patch changes the default compression level to 9 to have the
minimum image size.

Change-Id: Id20292e73796b2c0d72a4d3f5279e02fc3a2757a

ironic_python_agent_builder/__init__.py

@@ -80,7 +80,7 @@ def main():
         os.environ['DIB_REPOREF_requirements'] = args.branch
     if args.lzma:
         os.environ['DIB_IPA_COMPRESS_CMD'] = \
-            'xz --format=lzma --compress --stdout'
+            'xz --format=lzma --compress --stdout -9'
     # Enable checksum generation by default
     if 'DIB_CHECKSUM' not in os.environ:
         os.environ['DIB_CHECKSUM'] = 'sha256'

releasenotes/notes/lzma-compression-level-1ca346ba8d5b905a.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Changes lzma compression level to 9 for smaller images.