depends: add ability to skip building qrencode

Summary:

Similar to other depends packages, add the ability to skip building
qrencode by passing NO_QR=1.

Backport of core PR17658.

Test Plan:

make build-osx NO_QR=1

Check the qrencode lib is not built.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5664