* Makefile.in (distdir): Handle absolute $distdir.

Avoid using the GNU extension $^.

* examples/Makefile.in: Avoid using the GNU extension $^.
* tools/Makefile.in: Likewise.
* testsuite/Makefile.in: Likewise.

Rev: src/nettle/ChangeLog:1.308
Rev: src/nettle/Makefile.in:1.15
Rev: src/nettle/examples/Makefile.in:1.10
Rev: src/nettle/testsuite/Makefile.in:1.10
Rev: src/nettle/tools/Makefile.in:1.11