Did you recompile everything? Some version of the 6.x compilers had a __pgi_trace symbol. This has been changed in later compilers. You should really recompile when changing major version numbers.
My guess is that you’re using gcc to link idt. Try either using pgcc or add the linker script “/opt/pgi/linux86/7.0/lib/pgi.ld” to you link options.
The “__pgi_trace” symbol was added as of the 6.2 release in order to support on demand trace back debugging. Unfortunately, this addition has caused some compatability issues with non-PGI compilers.