Bug#1015651: riemann-c-client: ftbfs with LTO (link time optimization) enabled

[Gergely Nagy <gergo@csillger.hu>]

    Matthias> The full build log can be found at:
    Matthias> http://qa-logs.debian.net/2022/06/09/dpkglto/riemann-c-client_1.10.4-2_unstable_dpkglto.log
    Matthias> The last lines of the build log are at the end of this report.

    Matthias> [...]
    Matthias> libtool: link: gcc -shared  -fPIC -DPIC  lib/riemann/.libs/libriemann_client_la-client.o lib/riemann/client/.libs/libriemann_client_la-tcp.o lib/riemann/client/.libs/libriemann_client_la-tls.o lib/riemann/client/.libs/libriemann_client_la-udp.o lib/riemann/.libs/libriemann_client_la-event.o lib/riemann/.libs/libriemann_client_la-message.o lib/riemann/.libs/libriemann_client_la-attribute.o lib/riemann/.libs/libriemann_client_la-query.o lib/riemann/.libs/libriemann_client_la-simple.o lib/riemann/proto/.libs/libriemann_client_la-riemann.pb-c.o   -lprotobuf-c -lgnutls  -g -O2 -flto=auto -fstack-protector-strong -Wl,--version-script -Wl,../../lib/riemann/libriemann.ver -flto=auto -Wl,-z -Wl,relro -Wl,-z -Wl,now   -Wl,-soname -Wl,libriemann-client.so.0 -o lib/.libs/libriemann-client.so.0.10.4
    Matthias> /tmp/ccyYWTmS.s: Assembler messages:
    Matthias> /tmp/ccyYWTmS.s: Error: invalid attempt to declare external version name as default in symbol `riemann_client_new@@RIEMANN_C_1.10'
    Matthias> make[3]: *** [/tmp/cc9nbBSc.mk:2:
    Matthias> /tmp/cchkO7Jq.ltrans0.ltrans.o] Error 1

FYI, this is fixed upstream in riemann-c-client 2.x, however, that
version is ABI incompatible with 1.x, so dependent packages will need to
be recompiled, transitioned, etc.

The problem appears to be that riemann-c-client has two versions of the
`riemann_client_new` symbol, one tagged @RIEMANN_C_1.10, which should be
the default, and another tagged @RIEMANN_C_1.0. This is achieved by a
bit of trickery in lib/riemann/client.c, which appears to throw off LTO.
I have no idea how to make the two compatible, and I'm not convinced it
would be worth figuring out how to, either.

Disabling symbol versioning would fix the issue, but that would be an
ABI break. Since 2.0 broke ABI anyway, it's easier to upgrade there,
where the problem does not exist, as there aren't any symbols with
different versions there.

The other fix is to disable LTO for riemann-c-client, that is likely the
easiest way.

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