build flags in Makefile

[Robert Millan]

Hi,

Please forgive my ignorance on NetBSD make flags; does anyone know how to make 
the Rump build
system enable them?

E.g.

.if ${RUMP_PCI_IOSPACE:Uno} == "yes"
CPPFLAGS+=-DRUMP_PCI_IOSPACE
.endif

--
Robert Millan