cmake: fix up BOOST_IGNORE_SYSTEM_PATHS
cmake: fix up BOOST_IGNORE_SYSTEM_PATHS

The option was set twice when it only needs to be set once. Also fix a
bogus dereference and spurious whitespace.

eiabea/bitmonero,ranok/bitmonero,eiabea/bitmonero,ranok/bitmonero,ranok/bitmonero,ranok/bitmonero,eiabea/bitmonero,eiabea/bitmonero,eiabea/bitmonero,eiabea/bitmonero,ranok/bitmonero,ranok/bitmonero