main/xen,community/rng-tools: remove unicode whitespace from APKBUILDs

Fix bugs in 2 packages by removing Unicode whitespace.

I found these problems by parsing all APKBUILD scripts with my shell
(http://www.oilshell.org/).

The problem only occurs if 'make' fails.  Here is an excerpt:

$ od -c unicode-space.sh
0000000   m   a   k   e       |   | 302 240   r   e   t   u   r   n
0000020   1  \n
0000022

\302 \204 is a utf-8 whitespace.  No shells accept this -- it's parsed
as part of the 'return' word, which makes it an invalid command.

$ busybox ash unicode-space.sh
make: *** No targets specified and no makefile found.  Stop.
unicode-space.sh: line 1:  return: not found

$ bash unicode-space.sh
make: *** No targets specified and no makefile found.  Stop.
unicode-space.sh: line 1:  return: command not found

$ dash unicode-space.sh
make: *** No targets specified and no makefile found.  Stop.
unicode-space.sh: 1: unicode-space.sh:  return: not found

Remove '|| return 1' from lines that contained unicode whitespace.

abuild now runs with 'set -e'.