According to very brief documentation on https://www.qnx.com/developers/docs/6.4.1/neutrino/prog/using_gdb.html, the sequence of launching an executable to debug is
target qnx ...
upload ...
run
I.e. I am forced to upload a file to the target every time I start a gdb session. Is there a way I can debug executable already on the target?
Found it!
set nto-executable <path on target>