This makes it easier to run the uninstalled daemon.
* nix/local.mk (libstore_a_CPPFLAGS): Append "/guix" to
NIX_LIBEXEC_DIR.
* build-aux/pre-inst-env.in (NIX_LIBEXEC_DIR): Adjust comment.
* nix/libstore/builtins.cc (builtinDownload): Remove SUBDIR and its
use.
* nix/libstore/local-store.cc (runAuthenticationProgram): Ditto.
* nix/libstore/gc.cc (addAdditionalRoots): Remove "/guix" prefix.
* nix/nix-daemon/guix-daemon.cc (main): Ditto.
This prevents libstore/build.cc from executing nix/scripts/offload, which is
always created by config.status, when offload support is not enabled.
* build-aux/pre-inst-env.in: Export 'NIX_BUILD_HOOK' only when
configured; unset it otherwise.
* pre-inst-env.in: Move to ...
* build-aux/pre-inst-env.in: ... here.
* test-env.in: Move to ...
* build-aux/test-env.in: ... here.
* configure.ac (AC_CONFIG_FILES): Adapt to this. Keep the generated
scripts in their current location which is $(top_builddir).