An attempt to normalize some of the function names in build.zig. Normalize add*Dir to add*Path. Also use "Library" instead of the "Lib" abbreviation.
The PR does not remove the old names, only adds the new normalized ones to faciliate a transition period.
Otherwise, for last sections in segments it could happen we would
not expand the segment when actually required thus exceeding the
segment's size and causing data clobbering and dyld runtime errors.