treewide: fix shell errors during dump stage

treewide: fix shell errors during dump stage

Fixes following issues:

 bash: -c: line 1: `echo 1686820180<LINUX_VERMAGIC> | /staging_dir/host/bin/mkhash md5 | cut -b1-8'
 bash: -c: line 1: `echo 1686820180<LINUX_VERMAGIC> | /staging_dir/host/bin/mkhash md5 | sed -E 's/(.{8})(.{4})(.{4})(.{4})(.{10})../\1-\2-\3-\4-\500/''
 bash: -c: line 1: syntax error near unexpected token `|'
 bash: line 1: *1024*1024: syntax error: operand expected (error token is "*1024*1024")
 bash: line 1: (64 + ): syntax error: operand expected (error token is ")")
 expr: syntax error: missing argument after '+'

Signed-off-by: Petr Štetiar <ynezz@true.cz>
(cherry picked from commit 8fc496be860192f8bd1f16913657626014c8863f)
[ fix merge conflicts, adapt to 22.03 ]
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>