minimal/do: some shells return error in "read x <file" for empty files.

...or files that contain bytes but not a trailing newline.  It's okay if we
don't get any data, but we definitely have to *not* let "set -e" abort us.
Now that we fixed set -e in the previous patch, it revealed this problem.

minimal/do

@@ -94,7 +94,7 @@ _run_dofile()
 	export REDO_TARGET=$PWD/$target
 	local line1
 	set -e
-	read line1 <"$PWD/$dofile"
+	read line1 <"$PWD/$dofile" || true
 	cmd=${line1#"#!/"}
 	if [ "$cmd" != "$line1" ]; then
 		/$cmd "$PWD/$dofile" "$@" >"$tmp.tmp2"