* Install the worker in bindir, not libexecdir.

* Allow the worker path to be overriden through the NIX_WORKER
  environment variable.

src/libmain/Makefile.am

@@ -9,6 +9,7 @@ AM_CXXFLAGS = \
  -DNIX_LOG_DIR=\"$(localstatedir)/log/nix\" \
  -DNIX_CONF_DIR=\"$(sysconfdir)/nix\" \
  -DNIX_LIBEXEC_DIR=\"$(libexecdir)\" \
+ -DNIX_BIN_DIR=\"$(bindir)\" \
  -DNIX_VERSION=\"$(VERSION)\" \
  -I$(srcdir)/.. ${aterm_include} -I$(srcdir)/../libutil \
  -I$(srcdir)/../libstore