Getting rid of duplicate symbols during linking

I am porting another programmers library to the IBMi and attempting to link
a tiny main program to a service program that I have built via a makefile.
I have never built a service program myself before so I'm trying to learn
something new. During the linking stage I get these messages:

Definition supplied multiple times for symbol
'__nw__FUiPv'.
Definition supplied multiple times for symbol
'__dftbdt__Q2_3std12codecvt_baseFv'.
Definition supplied multiple times for symbol
'__dftbdt__Q2_3std10ctype_baseFv'.

Currently in our production code we use *DUPVAR, *DUPPROC, and *NOWARN but
we are really trying to tighten the ship and get our code to compile
cleaner. These symbols appear to come from standard library stuff, I
assume, since they don't look familiar to me. Are there any techniques I
can use to track down the code that generates these symbols then kill and
destroy them? :-)

I am using DSPMOD library/module DETAIL(*EXPORT *IMPORT) via QSH & IFS and
redirecting all of this to a file, so I can search for these symbols and I
know where they exist.

FWIW, I am using the 'icc' compiler that is part of the 5799-PTL package.
It is just a front-end to CRTCPPMOD & CRTPGM. I am also using a makefile &
the 'gmake' command, along with 'ld' and 'qar'.