The ornamental design for a buildingextrusion, as shown and described.
FIG. 1 is a front end view of a building extrusion, showing our new design;
FIG. 2 is a back end view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a front, bottom and left side perspective view thereof.
Broken lines are used in the drawings to illustrate features of the building extrusion that form no part of the claimed design. The building extrusion is shown with a symbolic break in its length. The appearance of any portion of the building extrusion between the break lines forms no part of the claimed design.