Comment # 3 on bug 1204697 from Martin Li������ka

(In reply to Egbert Eich from comment #2)
> Ok, static libraries require the -ffat-lto-objects on the compiler command
> line when doing LTO builds.
> 
> Easiest solution: expand the _lto_cflags definition:
> 
> %if "%{?_lto_cflags}" != ""
> %global _lto_cflags %{_lto_cflags} -ffat-lto-objects
> %endif

Yes, that's the common approach:
https://en.opensuse.org/openSUSE:LTO#Static_libraries

> 
> If we'd shipped the object directly in the RPM this problem would have
> occurred immediately as the object would have been subject to stripping
> during install post-processing. In this case, the objects would not have
> destroyed reproducibility. 
> Since this would have caused all sorts of warnings, the entire test suite
> was wrapped in a tar ball which we extract when installing the package.

Yes, stripping of LTO byte-code happens automatically and is done with the
following script:
https://github.com/openSUSE/brp-check-suse/blob/master/brp-15-strip-debug