That means the bootloader wasn't active. Make sure to press the button on the Trinket to activate the bootloader before clicking the Upload button.
Check that you updated the avrdude.conf file above - if you don't update the description of the Attiny85 in the configure file by replacing it, the IDE wont know to be patient with the Trinket/Gemma bootloader and will have many upload errors
These can generally be ignored and should not interfere with the program upload. Unfortunately Linux's USB core is a little flakey communicating with the ATtiny85 processor on the Trinket/Gemma and can cause these errors. If an upload does fail, try it again as it is likely an intermittent issue.