Comment # 13 on bug 1133294 from Martin Li������ka

(In reply to Stefan Dirsch from comment #12)
> Hmm. I don't know how to do this just for the subtree test/. Maybe I can
> figure out if I would know which gcc options
> this "_lto_cflags" manipulates (currently used in specfile: "%define
> _lto_cflags %{nil}"). Then I could adjust Makefile.am below tests/

Looking at build log, the tests are build as part of:

[   90s] + make -j8
[   90s] Making all in doc
[   90s] make[1]: Entering directory
'/home/abuild/rpmbuild/BUILD/xserver-1.20.10/doc'
...

what you can do is to add -fno-lto in test/Makefile (adding that to
C{,CXX}FLAGS}.