uninative-tarball.xz - reproducibility fix

added --clamp-mtime --mtime to the tar command

see:
https://bugzilla.yoctoproject.org/show_bug.cgi?id=15148

(From OE-Core rev: 2ef7c63871ab4fb62a9cea45a23a78bf9d541e4a)

Signed-off-by: Robert Berger <Robert.Berger@ReliableEmbeddedSystems.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes-recipe/populate_sdk_base.bbclass

@@ -285,7 +285,7 @@ python check_sdk_sysroots() {
     dir_walk(SCAN_ROOT)
 }
 
-SDKTAROPTS = "--owner=root --group=root"
+SDKTAROPTS = "--owner=root --group=root --clamp-mtime --mtime=@${SOURCE_DATE_EPOCH}"
 
 fakeroot archive_sdk() {
 	# Package it up