configure.ac is missing, so need to edit this manually

https://bugs.gentoo.org/870646
--- a/configure
+++ b/configure
@@ -796,3 +796,3 @@
 
-main(){return(0);}
+int main(void){return(0);}
 EOF
@@ -1100,3 +1100,3 @@
 #include "confdefs.h"
-main()
+int main(void)
 				{exit(sizeof(void*)==8 ? 0 : sizeof(void*));}
@@ -1463,3 +1463,3 @@
 #include <sys/types.h>
-main()
+int main(void)
 {
@@ -3330,3 +3330,3 @@
 #define min(a,b) ((a) < (b) ? (a) : (b))
-main()
+int main(void)
 {
@@ -3596,3 +3596,3 @@
 #include "include/dcc_paths.h"
-main()
+int main(void)
 {