The ornamental design for a buildingextrusion, as shown and described.
FIG. 1 is a front end view of a building extrusion, showing my new design;
FIG. 2 is a back end view thereof;
FIG. 3 is a right side elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a magnified view of the area identified in FIG. 4;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a perspective view thereof.
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.