can i manual download protobuf when cross-compilation on ubuntu #11805

<!-- This issue tracker is only for technical issues related to Bitcoin Core. General bitcoin questions and/or support requests are best directed to the Bitcoin StackExchange at https://bitcoin.stackexchange.com. For reporting security issues, please read instructions at https://bitcoincore.org/en/contact/. If the node is "stuck" during sync or giving "block checksum mismatch" errors, please ensure your hardware is stable by running memtest and observe CPU temperature with a load-test tool such as linpack before creating an issue! -->

<!-- Describe the issue -->

<!--- What behavior did you expect? -->

<!--- What was the actual behavior (provide screenshots if the issue is GUI-related)? -->

<!--- How reliably can you reproduce the issue, what are the steps to do so? -->

<!-- What version of Bitcoin Core are you using, where did you get it (website, self-compiled, etc)? -->

<!-- What type of machine are you observing the error on (OS/CPU and disk type)? -->

<!-- Any extra information that might be useful in the debugging process. -->

<!--- This is normally the contents of a `debug.log` or `config.log` file. Raw text or a link to a pastebin type site are preferred. -->

when i execute the cmd make HOST=x86_64-w64-mingw32, it will download the protobuf package, but on my ubuntu environment, it cannot download it because of no proxy, so i want to ask that is it possible to download manual first and where to put it?

In the event you download protobuf manually, you'd need to place it in /usr/include. Alternatively, you could run this script: https://gist.github.com/sofyanhadia/37787e5ed098c97919b8c593f0ec44d8.

You can the tarball in depends/sources. No need to install it system-wide. Easiest way to get the correct versions is to do make download in depends on a computer that does have internet access, then copy that directory.