Makefile: fix VPATH (out-of-tree) builds.
In librsvg/rsvg.h
, the include is "librsvg-enum-types.h", which is a
generated file and is therefore inside $(top_builddir)/librsvg/.
In librsvg/rsvg.h
, the include is "librsvg-enum-types.h", which is a
generated file and is therefore inside $(top_builddir)/librsvg/.