Detect tarantool as the Lua interpreter

This change eliminates the following warning when tarantool is the only
Lua interpreter installed on the system:

> Warning: Could not find a Lua interpreter for version 5.1 in your
> PATH. Modules may not install with the correct configurations. You may
> want to specify to the path prefix to your build of Lua 5.1 using
> --lua-dir

src/luarocks/util.lua

@@ -438,7 +438,14 @@ do
       if not util.exists(lua_exe) then
          return nil
       end
-      local lv, err = util.popen_read(Q(lua_exe) .. ' -e "io.write(_VERSION:sub(5))"')
+
+      local cmd = 'io.write(_VERSION:sub(5))'
+      -- Tarantool falls into the interactive mode if no script is
+      -- given even when -e option is passed.
+      if lua_exe:find('tarantool') then
+         cmd = cmd .. ' os.exit()'
+      end
+      local lv, err = util.popen_read(Q(lua_exe) .. (' -e "%s"'):format(cmd))
       if lv == "" then
          return nil
       end
@@ -457,7 +464,12 @@ do
 
       local ljv
       if cfg.lua_version == "5.1" then
-         ljv = util.popen_read(Q(cfg.variables["LUA_BINDIR"] .. "/" .. cfg.lua_interpreter) .. ' -e "io.write(tostring(jit and jit.version:gsub([[^%S+ ]], [[]])))"')
+         local cmd = 'io.write(tostring(jit and jit.version:sub(8)))'
+         -- Exit from the iteractive mode. See the comment above.
+         if lua_exe:find('tarantool') then
+            cmd = cmd .. ' os.exit()'
+         end
+         ljv = util.popen_read(Q(lua_exe) .. (' -e "%s"'):format(cmd))
          if ljv == "nil" then
             ljv = nil
          end
@@ -494,6 +506,7 @@ do
          end
          if luaver == "5.1" or not luaver then
             table.insert(names, "luajit" .. exe_suffix)
+            table.insert(names, "tarantool")
          end
          table.insert(names, "lua" .. exe_suffix)