Add information on building of pull requests to HACKING
Add information on building of pull requests to HACKING

9fcc/check,9fcc/check,9fcc/check,brarcher/check,brarcher/check,libcheck/check,libcheck/check,krichter722/check,brarcher/check,krichter722/check,brarcher/check,brarcher/check,krichter722/check,9fcc/check,libcheck/check,krichter722/check,libcheck/check,9fcc/check,libcheck/check,krichter722/check