Compiling gnumeric-1.8.0 on OS X, with all support libs supplied by fink, in plugins/python-loader:

/bin/sh ../../libtool --tag=CC   --mode=link gcc  -g -O2 -Wall -Wmissing-prototypes  -Wsign-compare -Wpointer-arith -Wnested-externs -Wchar-subscripts -Wwrite-strings -Wdeclaration-after-statement -Wnested-externs -Wmissing-noreturn -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wno-pointer-sign -module -avoid-version  -L /sw/lib -lpython2.5 -L/sw/lib/python2.5/config   -L/sw/lib -o python_loader.la -rpath /sw/lib/gnumeric/1.8.0/plugins/python-loader python-loader.lo gnm-python.lo gnm-py-interpreter.lo py-gnumeric.lo py-interpreter-selector.lo py-command-line.lo py-console.lo boot.lo  
gcc ${wl}-undefined ${wl}dynamic_lookup -o .libs/python_loader.so -bundle  .libs/python-loader.o .libs/gnm-python.o .libs/gnm-py-interpreter.o .libs/py-gnumeric.o .libs/py-interpreter-selector.o .libs/py-command-line.o .libs/py-console.o .libs/boot.o  -L/sw/src/fink.build/gnumeric-1.8.0-2/gnumeric-1.8.0/plugins/python-loader -lpython2.5 -L/sw/lib/python2.5/config -L/sw/lib
creating python_loader.la

There are no -l flags for gobject or any other glib/gtk stuff, even though many symbols are used from those libs. The problem is in configure.in, starting at line 944 (as of 1.8.0; SVN trunk is same):

    PKG_CHECK_MODULES(PYGOBJECT, pygobject-2.0 >= pygobject_required_version,,
      [python_msg="Missing pygobject"])
[...]
    GNM_PY_CFLAGS="-I $PY_INCLUDE_DIR $PYGOBJECT_CFLAGS"
    GNM_PY_LDFLAGS="-L $PY_LIB_DIR -lpython$PY_VERSION $PYGOBJECT_LDFLAGS"

It *looks* reasonable, but PKG_CHECK_MODULES(FOO) sets FOO_CFLAGS and FOO_LIBS, not FOO_LDFLAGS. So instead, that last line above should be:

    GNM_PY_LDFLAGS="-L $PY_LIB_DIR -lpython$PY_VERSION $PYGOBJECT_LIBS"