ext/json/parser/prereq.mk: keep line numbers of ext/json/parser/parser.c

Follow up of 5717e55e9a.
Adding a header with newline broke linenos.

ext/json/parser/parser.c

@@ -1,5 +1,4 @@
 /* This file is automatically generated from parser.rl by using ragel */
-
 #line 1 "parser.rl"
 #include "../fbuffer/fbuffer.h"
 #include "parser.h"

ext/json/parser/prereq.mk

@@ -6,6 +6,6 @@ RAGEL = ragel
 	$(RAGEL) -G2 $<
 	$(BASERUBY) -pli -e '$$_.sub!(/[ \t]+$$/, "")' \
 	-e '$$_.sub!(/^static const int (JSON_.*=.*);$$/, "enum {\\1};")' \
-	-e '$$header ||= $$_ = "/* This file is automatically generated from parser.rl by using ragel */\n" + $$_' $@
+	-e '$$header ||= $$_ = "/* This file is automatically generated from parser.rl by using ragel */" + $$_' $@
 
 parser.c: