Jenkins incoherence

[Lionel Elie Mamane]

https://ci.libreoffice.org/job/lo_gerrit/25062/
looks like Jenkins build different code on (Windows and MacOS X) vs
GNU/Linux. Given the error on the GNU/Linux builds, I don't understand
how any other platform could build. At first I thought Jenkins build
without Firebird on MacOS X and Windows, but the build log shows
connectivity/source/drivers/firebird being built.

Indeed:

git checkout -f adf948a0895896976b138fb2e81c8b558c7af68f # timeout=30
vs
git checkout -f be4f19381ef0ae17c6ef964740fc671258ed0b78 # timeout=30