Add build directory to git ignore.
Add build directory to git ignore.

trcwm/openpnp-capture,openpnp/openpnp-capture,trcwm/openpnp-capture,openpnp/openpnp-capture,openpnp/openpnp-capture,trcwm/openpnp-capture,openpnp/openpnp-capture,trcwm/openpnp-capture,trcwm/openpnp-capture,openpnp/openpnp-capture,openpnp/openpnp-capture,trcwm/openpnp-capture