cmake: do not ignore dangerous warnings with -Wno-error
cmake: do not ignore dangerous warnings with -Wno-error

Shorten the list of warnings that are reported, but
which are forced to NOT generate an error, via -Wno-error.

Unwhitelist these: strict-aliasing, sign-compare, type-limits

For example, ignoring strict-aliasing warning caused
lots of wasted time diagnosing Issue #847.

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