An 87-year-old Westford man has died after succumbing to injuries he received during a car crash that involved a police cruiser. Thomas Courtney was a passenger in a pickup truck that struck a Westford police cruiser on Oak Hill Road on Aug. 29, the Middlesex district attorney’s office said. Courtney, who was hospitalized, died on Monday. The driver, whose name has not been released, has not been charged in the crash, which is still under investigation, said Stephanie Guyotte, spokeswoman for the Middlesex district attorney’s office. The officer in the police cruiser was not injured.