lib9: declare __fixargv0 before use in flag.c

The Plan 9 compilers complain about not
having type information for the function,
which sets off type signature problems
during the linking stage.

R=rsc, ality, iant
CC=golang-dev
https://golang.org/cl/7058054

src/lib9/argv0.c

-/*
-Plan 9 from User Space src/lib9/argv0.c
-http://code.swtch.com/plan9port/src/tip/src/lib9/argv0.c
-
-Copyright 2001-2007 Russ Cox.  All Rights Reserved.
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in
-all copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-THE SOFTWARE.
-*/
-
-#include <u.h>
-#include <libc.h>
-
-char *argv0;
-
-/*
- * Mac OS can't deal with files that only declare data.
- * ARGBEGIN mentions this function so that this file gets pulled in.
- */
-void __fixargv0(void) { }

src/lib9/flag.c

@@ -26,6 +26,14 @@ static Flag *curflag;
 static Flag *fhash[512];
 static Flag *first, *last;
 
+char *argv0;
+
+/*
+ * Mac OS can't deal with files that only declare data.
+ * ARGBEGIN mentions this function so that this file gets pulled in.
+ */
+void __fixargv0(void) { }
+
 // FNV-1 hash. http://isthe.com/chongo/tech/comp/fnv/
 static uint32
 fnv(char *p, int n)
@@ -221,7 +229,6 @@ flagparse(int *argcp, char ***argvp, void (*usage)(void))
 	argc = *argcp;
 	argv = *argvp;
 
-	__fixargv0();
 	argv0 = argv[0];
 	argc--;
 	argv++;