Update vlib/builtin/cfns.c.v

Co-authored-by: Delyan Angelov <delian66@gmail.com>

Author: enghitalo

vlib/builtin/cfns.c.v

@@ -12,7 +12,7 @@ fn C.memmove(dest voidptr, const_src voidptr, n usize) voidptr
 
 fn C.memset(str voidptr, c int, n usize) voidptr
 
-fn C.memchr(buf &u8, char int, len usize) &u8
+fn C.memchr(str voidptr, c int, n usize) voidptr
 
 @[trusted]
 fn C.calloc(int, int) &u8