Handle environment variables with spaces in craftenv.sh

Summary:
craftenv.sh converts the CraftSetupHelper.py output to a bash array which
will split on any whitespace. Now only split on newlines.

This fixes my $PS1 being chopped off after the first space.

Test Plan: environment variables with spaces are no longer broken.

Reviewers: vonreth

Reviewed By: vonreth

Differential Revision: https://phabricator.kde.org/D11576