systemd version the issue has been seen with

239

Used distribution

CentOS 7

Expected behaviour you didn't see
The build should either fail and clarify the missing dependency, or disable the DNS-over-TLS feature

Unexpected behaviour you saw

../src/resolve/resolved-dns-transaction.c:17:27: fatal error: gnutls/socket.h: No such file or directory
#include <gnutls/socket.h>
                          ^
compilation terminated.

Steps to reproduce the problem
When DNS-over-TLS is enabled, src/resolve/resolved-dns-transaction.c includes gnutls/socket.h, which was added in gnutls/gnutls@0f67cce#diff-d468b0837d8f0c1f2c70b0252c105a6a and is not available in gnutls 3.1.4 (which is the one we test for in meson). I noticed this because CentOS 7 ships with 3.3.26, which is also missing the include.