In openSUSE Tumbleweed (and several other distributions as well),
packages are build by default with linktime optimization (LTO)
enabled. This didn´t work for Dovecot, so until now LTO was disabled
for Dovecot. There is a way to make it work though, see the following
link:

 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=997513#20

So far a fix has not made it to upstream, the latest version 2.3.30
still fails to build without this patch. Is there any news to report
regarding this?