angstrom-version: fix quoting in /etc/os-release

It turns out that this file is meant to be sourcable by the shell, leading to errors like this:

	*** Including module: base ***
	/etc/os-release: line 3: $'\303\205ngstr\303\266m': command not found
	/etc/os-release: line 4: 35: command not found

This fixes the above error when running dracut

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>