[installer]: Suppress tar xz warning about time stamp in the future, …

…if date is not correctly set (#1560)

Signed-off-by: Qi Luo <qiluo-msft@users.noreply.github.com>

installer/x86_64/install.sh

@@ -446,7 +446,11 @@ fi
 # Decompress the file for the file system directly to the partition
 unzip -o $ONIE_INSTALLER_PAYLOAD -x "$FILESYSTEM_DOCKERFS" -d $demo_mnt/$image_dir
 
-TAR_EXTRA_OPTION="--numeric-owner"
+if [ "$install_env" != "build" ]; then
+    TAR_EXTRA_OPTION="--numeric-owner"
+else
+    TAR_EXTRA_OPTION="--numeric-owner --warning=no-timestamp"
+fi
 mkdir -p $demo_mnt/$image_dir/$DOCKERFS_DIR
 unzip -op $ONIE_INSTALLER_PAYLOAD "$FILESYSTEM_DOCKERFS" | tar xz $TAR_EXTRA_OPTION -f - -C $demo_mnt/$image_dir/$DOCKERFS_DIR