config.h: idempotent-wrap the generated config.h

config.h

+#ifndef CCAN_CONFIG_H
+#define CCAN_CONFIG_H
 /* Generated by CCAN configurator */
 #define CCAN_COMPILER "cc"
 #define CCAN_CFLAGS "-g -Wall -Wstrict-prototypes -Wold-style-definition -Wmissing-prototypes -Wmissing-declarations"
@@ -34,3 +36,4 @@
 #define HAVE_TYPEOF 1
 #define HAVE_UTIME 1
 #define HAVE_WARN_UNUSED_RESULT 1
+#endif /* CCAN_CONFIG_H */

tools/configurator/configurator.c

@@ -337,10 +337,13 @@ int main(int argc, char *argv[])
 	unlink(INPUT_FILE);
 
 	cmd[strlen(cmd) - strlen(" -o " OUTPUT_FILE " " INPUT_FILE)] = '\0';
-	printf("/* Generated by CCAN configurator */\n");
+	printf("#ifndef CCAN_CONFIG_H\n"
+	       "#define CCAN_CONFIG_H\n"
+	       "/* Generated by CCAN configurator */\n");
 	printf("#define CCAN_COMPILER \"%s\"\n", argv[1]);
 	printf("#define CCAN_CFLAGS \"%s\"\n\n", cmd + strlen(argv[1]) + 1);
 	for (i = 0; i < sizeof(tests)/sizeof(tests[0]); i++)
 		printf("#define %s %u\n", tests[i].name, tests[i].answer);
+	printf("#endif /* CCAN_CONFIG_H */\n");
 	return 0;
 }