There is no overloaded function for swap(unsigned long). big endian archs
fix for: riscv/byteorder.h:22:58: error: call to 'swap' is ambiguous

Index: fesvr/syscall.cc
--- fesvr/syscall.cc.orig
+++ fesvr/syscall.cc
@@ -300,7 +300,7 @@ reg_t syscall_t::sys_getmainvars(reg_t pbuf, reg_t lim
 {
   std::vector<std::string> args = htif->target_args();
   std::vector<uint64_t> words(args.size() + 3);
-  words[0] = to_le(args.size());
+  words[0] = to_le((uint32_t) args.size());
   words[args.size()+1] = 0; // argv[argc] = NULL
   words[args.size()+2] = 0; // envp[0] = NULL