enable expensive hardening message is wrong with static library builds

A user complained on IRC that using expensive hardening and static builds together resulted in this warning:

configure: error: The compiler supports -fsanitize=address, but for some reason I was not able to link when using it. Are you missing run-time support? With GCC you need libubsan.so, and with Clang you need libclang_rt.ubsan*

We should say that you need "libubsan.*" for GCC, because you need the static version for static builds.