bash: Remove unnecessary 'Makefile.inc' that is keeping reference to bootstrap-tools

The file is an example makefile for developing bash plugins, and
contains stuff like:

````
example:	example.o
	$(SHOBJ_LD) $(SHOBJ_LDFLAGS) $(SHOBJ_XLDFLAGS) -o $@ example.o $(SHOBJ_LIBS)
````

So no package is really going to depend on that, and it's making the
.dev output keep a reference to the bootstrap tools. Just nuke it.