Fix Ninja build failing in the pipeline

Currently, Ninja seems to fail in the nightly pipeline with the following error:

[323/1010] Building CXX object tapeserver/castor/tape/tapeserver/daemon/CMakeFiles/ctatapeserverdaemonunittests.dir/DataTransferSessionTest.cpp.o
FAILED: tapeserver/castor/tape/tapeserver/daemon/CMakeFiles/ctatapeserverdaemonunittests.dir/DataTransferSessionTest.cpp.o 
/usr/bin/c++ -Dctatapeserverdaemonunittests_EXPORTS -I/builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00 -I/builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/build -I/usr/include/shift -I/builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/tapeserver -I/builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/tapeserver/h -I/builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/build/tapeserver -fPIC -pedantic -Wall -Wextra -Werror -Wno-unused-parameter -fstack-protector-all -std=c++17 -g -fPIC -MD -MT tapeserver/castor/tape/tapeserver/daemon/CMakeFiles/ctatapeserverdaemonunittests.dir/DataTransferSessionTest.cpp.o -MF tapeserver/castor/tape/tapeserver/daemon/CMakeFiles/ctatapeserverdaemonunittests.dir/DataTransferSessionTest.cpp.o.d -o tapeserver/castor/tape/tapeserver/daemon/CMakeFiles/ctatapeserverdaemonunittests.dir/DataTransferSessionTest.cpp.o -c /builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/tapeserver/castor/tape/tapeserver/daemon/DataTransferSessionTest.cpp
In file included from /builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/objectstore/Agent.hpp:20,
                 from /builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/scheduler/OStoreDB/OStoreDBFactory.hpp:24,
                 from /builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/tapeserver/castor/tape/tapeserver/daemon/DataTransferSessionTest.cpp:70:
/builds/cta/CTA/build_rpm/RPM/BUILD/cta-5-7851384gite0b67a00/objectstore/ObjectOps.hpp:24:10: fatal error: objectstore/cta.pb.h: No such file or directory
   24 | #include "objectstore/cta.pb.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

At first glance, this seems to have something to do with the protobuf file not being generated