The ornamental design for a toybuildingblock, as shown and described.
FIG. 1 is a perspective view of a toy building block showing the design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a left elevation view thereof;
FIG. 7 is a right elevation view thereof;
FIG. 8 is a sectional view through FIG. 2 at 8—8;
FIG. 9 is a sectional view through FIG. 2 at 9—9; and,
FIG. 10 is a perspective view thereof, together with a plurality of other like blocks, shown in broken lines, and forming no part of the claimed design.