build: if cross-compiling for an apple host, locate some additional tools
build: if cross-compiling for an apple host, locate some additional tools

This should be safe to do for native builds too, but for now it's
specific to cross-builds to avoid possible regressions.

peercoin/peercoin,ppcoin/ppcoin,peercoin/peercoin,ppcoin/ppcoin,peercoin/peercoin,DigitalPandacoin/pandacoin,peercoin/peercoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,peercoin/peercoin,ppcoin/ppcoin,ppcoin/ppcoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,peercoin/peercoin