Look for crates in LIBDIR, provided by --libdir option

Fixies #11671

This commit changes default relative libdir 'lib' to a relative libdir calculated using LIBDIR provided by --libdir configuration option. In case if no option was provided behavior does not change.

It should not be done this way. libdir from configure should be used during installation. Otherwise it will be for sure broken. install.sh parameters are passed by make, not by user. and make takes it from configuration.

I see no reason for user try to somehow use different libdirs in configuration and installation. And in my changes libdir is relative, so copying of the whole tree with compiler will work, if you would wondering about it.