[PATCH] sstate: Use -m option to tar when unpacking sstate

[Richard Purdie <richard.purdie@linuxfoundation.org>]

We've noticed failures on the project autobuilders where a shared sstate
directory is used across multiple builders and the clocks become skewed.

Most of the time this causes harmless building but if this happens where
an environment is changed (make install vs make in qt4-x11-free for example),
the build can fail.

This avoids modification times in the future and should make builds safer
in shared environments sstate was designed for.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
diff --git a/meta/classes/sstate.bbclass b/meta/classes/sstate.bbclass
index 3fcaa65..b60c766 100644
--- a/meta/classes/sstate.bbclass
+++ b/meta/classes/sstate.bbclass
@@ -544,7 +544,7 @@ sstate_create_package () {
 sstate_unpack_package () {
 	mkdir -p ${SSTATE_INSTDIR}
 	cd ${SSTATE_INSTDIR}
-	tar -xvzf ${SSTATE_PKG}
+	tar -xmvzf ${SSTATE_PKG}
 }
 
 # Need to inject information about classes not in the global configuration scope