native X, linux and $(prefix)

[Mark Davies <mark%ecs.vuw.ac.nz@localhost>]

I've just switched my linux builds from using "modular" X to using 
"native" so I've put the following in my mk.conf

X11_TYPE=native
X11BASE=/usr

and so far most things seem to be building OK but I've struck what 
appears to be the same problem in two packages  cairo-gobject and 
poppler-utils.  Both are instances where part of a build has been 
split off into separate packages and makefiles have been patched to 
use an installed library rather than one within the build.

eg.

 libcairo_gobject_la_LDFLAGS = -version-info 
$(CAIRO_LIBTOOL_VERSION_INFO) -no-undefined $(export_symbols)
-libcairo_gobject_la_LIBADD = $(top_builddir)/src/libcairo.la 
$(CAIRO_LIBS) $(GOBJECT_LIBS)
+libcairo_gobject_la_LIBADD = $(prefix)/lib/libcairo.la $(CAIRO_LIBS) 
$(GOBJECT_LIBS)
 all: all-am

the build then fails when trying to link that library because the path 
is wrong:

 CCLD   libcairo-gobject.la
libtool: link: cannot find the library 
`/local/scratch/pkgsrc/graphics/cairo-gobject/work.debretts/.x11-
buildlink/pkg/lib/libcairo.la' or unhandled argument 
`/local/scratch/pkgsrc/graphics/cairo-gobject/work.debretts/.x11-
buildlink/pkg/lib/libcairo.la'
*** Error code 1

Links to the library are in 
.../work.debretts/.x11-buildlink/lib/libcairo.la and
.../work.debretts/.buildlink/lib/libcairo.la

so where is the "/pkg/" part of the prefix coming from and why isnt 
this an issue on NetBSD with native X?

cheers
mark