The ornamental design for a buildingsensor, as shown and described.
FIG. 1 is a perspective view of a building sensor;
FIG. 2 is a front view of the building sensor;
FIG. 3 is a rear view of the building sensor;
FIG. 4 is a left view of the building sensor;
FIG. 5 is a right view of the building sensor;
FIG. 6 is a top view of the building sensor; and,
FIG. 7 is a bottom view of the building sensor.
The dash type broken lines in the Figures are for the purpose of illustrating unclaimed portions of the building sensor and form no part of the claimed design.