I don't know.
that's probably not the answer you expected, but I really don't know if there's a way to fix it.
I know there's a way to fix third party Classic Controllers (there's a patch somewhere buried in nintendont thread, or maybe on fix94 website) but I don't know if it would fix the non official wiimote or nunchuck too.
I'm not quite sure what to make of this since all other builds appear to use the same line. Missing library perhaps?
I never had this error, I thought you had another one (missing WUP library).
Maybe this is due to DevkitPPC r28 ?
try compiling with r27 (I still haven't updated my PPC revision, I don't know if it works and compile fine)
rename your "devkitpro/devkiptPPC", for example as "_r28" to the folder name.
Then download and extract r27 to your devkitpro folder.
another solution is to keep "devkitPPC" as latest revision and download/extract r27 as "devkitPPC_r27"
then before compiling, run this in your command line window :
set DEVKITPPC=/c/devkitpro/devkitppc_r27/
(or any other path you use)
it will temporarily set your devkitppc environment variable to the correct path. it will be set only for that command line window until you close it.
If installing r27 doesn't fix the error, be sure you used the portlib and libogc provided with the loader on sourceforge. you will have to run "make install" inside libs/wupc/ first.