build: Run `distcheck' with `--enable-daemon'.

* Makefile.am (AM_DISTCHECK_CONFIGURE_FLAGS): Add `--enable-daemon'.

Makefile.am

@@ -236,4 +236,5 @@ endif BUILD_DAEMON
 ACLOCAL_AMFLAGS = -I m4
 AM_DISTCHECK_CONFIGURE_FLAGS =			\
   --with-libgcrypt-prefix="$(LIBGCRYPT_PREFIX)"	\
-  --with-nix-prefix="$(NIX_PREFIX)"
+  --with-nix-prefix="$(NIX_PREFIX)"		\
+  --enable-daemon