Yes. You didn't follow their build instructions correctly. :-) In particular, you need to specify link dependencies after the dependent objects. Try this instead:
gcc -o guile-test `pkg-config guile-1.8 --cflags` guile-test.c `pkg-config guile-1.8 --libs`
In particular, the libraries need to be listed after all the objects that use them, such as guile-test.c
.
(By the way, this isn't Guile-specific. The standard linker always expects this ordering.)