external/libxmlsec: Pass down gb_VISIBILITY_FLAGS

...otherwise ASan build started to fail in CppunitTest_services with

> ==16664==ERROR: AddressSanitizer: odr-violation (0x7f4583587440):
>   [1] size=35 'xmlSecNs' strings.c:22:15
>   [2] size=35 'xmlSecNs' strings.c:22:15
> These globals were registered at these points:
>   [1]:
>     #0 0x44f410 in __asan_register_globals.part.11 /data/sbergman/github.com/llvm-project/llvm-project-20170507/compiler-rt/lib/asan/asan_globals.cc:358
>     #1 0x7f458295cded in asan.module_ctor (instdir/program/libxsec_gpg.so+0x197ded)
>
>   [2]:
>     #0 0x44f410 in __asan_register_globals.part.11 /data/sbergman/github.com/llvm-project/llvm-project-20170507/compiler-rt/lib/asan/asan_globals.cc:358
>     #1 0x7f45833cc28d in asan.module_ctor (instdir/program/libxsec_xmlsec.so+0x5da28d)
>
> ==16664==HINT: if you don't care about these errors you may set ASAN_OPTIONS=detect_odr_violation=0
> SUMMARY: AddressSanitizer: odr-violation: global 'xmlSecNs' at strings.c:22:15
> ==16664==ABORTING

after cae5f2a543b31552ccd9765aca5eb514fa694e07 "gpg4libre: initial GPG signature
generation"

Change-Id: I689241df52a7e878bfbd2d3dd6409bf0c104638b

0 files changed, 0 insertions, 0 deletions