rpm2cpio.sh: Don't drop newlines from header sizes

This script converts binary header sizes to decimal numbers. Shell is
not that well suited for this task as it drops newlines at the end of
command substitutions. Add a . character at the end and strip it right
after that to avoid this problem.

Resolves: rhbz#1983015

scripts/rpm2cpio.sh

@@ -27,7 +27,11 @@ calcsize() {
 
  i=0
  while [ $i -lt 8 ]; do
- b="$(_dd $(($offset + $i)) bs=1 count=1)"
+ # add . to not loose \n
+ # strip \0 as it gets dropped with warning otherwise
+ b="$(_dd $(($offset + $i)) bs=1 count=1 | tr -d '\0' ; echo .)"
+ b=${b%.} # strip . again
+
  [ -z "$b" ] &&
  b="0" ||
  b="$(exec printf '%u\n' "'$b")"