waf-cross-answers: Fix faulty link cross-answers-mipsel.txt

Apparently something was wrong in the patch "waf-cross-answers:
Add cross-answers-mipsel.txt". and it created a dead symlink.
Solve it by just copying the cross-answers-mips.txt instead of
linking it.

Fixes: 0898fb01



Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>