Fix for GCC 15.

From upstream: https://gmplib.org/repo/gmp/rev/d66d66d82dbb

--- gmp-6.3.0/acinclude.m4	2023-07-29 14:42:16.000000000 +0100
+++ gmp-6.3.0/acinclude.m4	2025-07-03 17:45:12.539771740 +0100
@@ -609,7 +609,7 @@
 
 #if defined (__GNUC__) && ! defined (__cplusplus)
 typedef unsigned long long t1;typedef t1*t2;
-void g(){}
+void g(int a,t1 const*b,t1 c,t2 d,t1 const*e,int f){}
 void h(){}
 static __inline__ t1 e(t2 rp,t2 up,int n,t1 v0)
 {t1 c,x,r;int i;if(v0){c=1;for(i=1;i<n;i++){x=up[i];r=x+1;rp[i]=r;}}return c;}