Seg fault on Windows in xmlsecurity_signing Unit Test

[Luke Benes]

Both my Windows box and @42 and @62 are failing with the following error:
[build CUT] xmlsecurity_pdfsigning
/usr/bin/sh: line 1:  8100 Segmentation fault      ( PATH="C:\core\instdir\program;C:\core\instdir\program;C:\core\workdir\LinkTarget\Library;C:\core\workdir\UnpackedTarball\cppunit\src\cppunit\ReleaseDll;$PATH" $W/LinkTarget/Executable/cppunittester.exe $W/LinkTarget/CppunitTest/test_xmlsecurity_signing.dll --headless "-env:BRAND_BASE_DIR=file:///$S/instdir" "-env:BRAND_SHARE_SUBDIR=share" "-env:BRAND_SHARE_RESOURCE_SUBDIR=program/resource" "-env:UserInstallation=file:///$W/CppunitTest/xmlsecurity_signing.test.user" "-env:CONFIGURATION_LAYERS=xcsxcu:file:///$I/share/registry xcsxcu:file:///$W/unittest/registry" "-env:UNO_TYPES=file:///$I/program/types.rdb file:///$I/program/types/offapi.rdb" "-env:UNO_SERVICES=file:///$W/Rdb/ure/services.rdb file:///$W/Rdb/services.rdb" -env:URE_INTERNAL_LIB_DIR=file:///$I/program -env:LO_LIB_DIR=file:///$I/program -env:LO_JAVA_DIR=file:///$I/program/classes --protector $W/LinkTarget/Library/unoexceptionprotector.dll unoexceptionprotector --protector $W/LinkTarget/Library/unobootstrapprotector.dll unobootstrapprotector --protector $W/LinkTarget/Library/vclbootstrapprotector.dll vclbootstrapprotector "-env:CPPUNITTESTTARGET=$W/CppunitTest/xmlsecurity_signing.test" ) > $W/CppunitTest/xmlsecurity_signing.test.log 2>&1
SigningTest::testDescription finished in: 1816ms

Error: a unit test failed, please do one of:
make CppunitTest_xmlsecurity_signing CPPUNITTRACE=TRUE 

https://tinderbox.libreoffice.org/cgi-bin/gunzip.cgi?tree=MASTER&brief-log=1540911001.21480


The failure started in this range: https://cgit.freedesktop.org/libreoffice/core/log/?qt=range&q=9ebcc7c9a21f33cf42146786e4463856d373f114..7b0f2ee441b0cbcb88f3020df40c49e7cd6f9fb1

Most likely this commit: 
https://cgit.freedesktop.org/libreoffice/core/commit/?id=9630a2dfc79b
external: upgrade libxmlsec to 1.2.27

Miklos,
Could you take a look at this?

-Luke