$(SAGE_LOCAL)/$(SPKG_INST_RELDIR)/xz-$(vers_xz)

----------
All lines of this file are ignored except the first.
It is copied by SAGE_ROOT/build/make/install into SAGE_ROOT/build/make/Makefile.

Adding the above instead of "xz" makes sure that the dependency is not replaced
by ".dummy".  In this way, liblzma delegates building to xz when
liblzma appears as a dependency.
