Build process: make clean attempts to preprocess GOB files

[Aaron Lehmann <aaronl@vitelus.com>]

Package: drgenius
Version: CVS

If you run 'make clean' before GOB has been built, the process will fail,
as it tries to create the gobobjs/*-mdi-child.c[c] files for the sole
purpose of deleting them. This seems like incorrect behavior anyway:

Making clean in gobobjs
make[1]: Entering directory `/home/aaronl/dr-genius/gobobjs'
./../gob/src/gob drgenius-mdi-child.gob
make[1]: ./../gob/src/gob: Command not found