Recent failing Gerrit Jenkins builds

[Stephan Bergmann]

Gerrit changes that are not based atop 
<https://gerrit.libreoffice.org/plugins/gitiles/core/+/4054a30e2b2fa254dfb20718ce757ceb2f638fd5%5E!/> 
"make: map slowcheck to gbuild's build and slowcheck" will fail in 
Jenkins, typically with a failure of CppunitTest_sw_xhtmlexport on 
Windows due to a missing 
instdir/share/xslt/export/xhtml/opendoc2xhtml.xsl.  (This is due to the 
recent rollout of 
<https://gerrit.libreoffice.org/plugins/gitiles/lode/+diff/a8c281cf47e8c162adf89d1cf3b2f9cebe620b29%5E%21> 
"change buildbot target to 'unitcheck slowcheck'" on the Jenkins machines.)

So just rebase your Gerrit changes that fail that way.