Add -m64 switch to gcc calls on 64-bit platforms.

gen/toobj.cpp

@@ -359,6 +359,10 @@ void assemble(const llvm::sys::Path& asmpath, const llvm::sys::Path& objpath)
     //FIXME: only use this if needed?
     args.push_back("-fpic");
 
+    //FIXME: enforce 64 bit
+    if (global.params.is64bit)
+        args.push_back("-m64");
+
     // Now that "args" owns all the std::strings for the arguments, call the c_str
     // method to get the underlying string array.  We do this game so that the
     // std::string array is guaranteed to outlive the const char* array.