[libvirt] [RFC PATCH] build: increase xz compression level

[Ján Tomko]

Increase the default compression level to 9 from 6.

This also increases decompression memory requirements
from 9 MB to 65 MB.
---
The resulting tarball is 880 kB smaller [10.5 MB]
Level 8 requires 33 MB and saves 520 kB [10.8 MB]
Level 7 requires 17 MB and saves 170 kB [11.2 MB]
Compression time is not much different since we're already using --extreme.

The Linux kernel also uses -9, but the tarball is 8x our size.

 cfg.mk | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/cfg.mk b/cfg.mk
index e93114c..ebafb0f 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -16,6 +16,9 @@
 # along with this program.  If not, see
 # <http://www.gnu.org/licenses/>.
 
+XZ_OPT ?= -9e
+export XZ_OPT
+
 # Use alpha.gnu.org for alpha and beta releases.
 # Use ftp.gnu.org for major releases.
 gnu_ftp_host-alpha = alpha.gnu.org
-- 
2.7.3