build: Add a comment above the sysvinit section.

* nix/local.mk (sysvinitservicedir): Add a comment.

Signed-off-by: Tobias Geerinckx-Rice <me@tobias.gr>

nix/local.mk

@@ -175,6 +175,7 @@ etc/guix-%.service: etc/guix-%.service.in	\
 	       "$<" > "$@.tmp";		\
 	mv "$@.tmp" "$@"
 
+# The service script for sysvinit.
 sysvinitservicedir = $(sysconfdir)/init.d
 nodist_sysvinitservice_DATA = etc/init.d/guix-daemon