Describe the issue

gitian-build.py --setup doesn't install curl, which is required by make download (which is run by gitian-build.py --build). Since some OS's like Debian Buster don't have curl installed by default, this causes a build error.

What behavior did you expect?

Bitcoin Core should build without errors in Gitian.

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

The following error shows up while trying to fetch Boost:

/bin/sh: 1: curl: not found

How reliably can you reproduce the issue, what are the steps to do so?

1. Install a fresh Debian Buster VM with KDE.
2. Clone Bitcoin Core.
3. ../bitcoin/contrib/gitian-build.py --commit --setup JeremyRand master
4. ../bitcoin/contrib/gitian-build.py --commit --build JeremyRand master

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

72634244580dc2e3c630ee27e47587080d064b68 , self-compiled.

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

Debian Buster VM inside Qubes OS; Haswell i7, HDD.

Any extra information that might be useful in the debugging process.

It looks like adding 'curl' to the programs list in gitian-build.py's setup function would be sufficient to solve the problem. 'wget' is already there.