/usr/include/casacore/casa/OS/ is in casacore-dev 2.2.0-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/casacore/casa/OS/CanonicalConversion.h
/usr/include/casacore/casa/OS/CanonicalDataConversion.h
/usr/include/casacore/casa/OS/Conversion.h
/usr/include/casacore/casa/OS/DOos.h
/usr/include/casacore/casa/OS/DataConversion.h
/usr/include/casacore/casa/OS/Directory.h
/usr/include/casacore/casa/OS/DirectoryIterator.h
/usr/include/casacore/casa/OS/DynLib.h
/usr/include/casacore/casa/OS/EnvVar.h
/usr/include/casacore/casa/OS/File.h
/usr/include/casacore/casa/OS/HostInfo.h
/usr/include/casacore/casa/OS/HostInfoBsd.h
/usr/include/casacore/casa/OS/HostInfoDarwin.h
/usr/include/casacore/casa/OS/HostInfoHpux.h
/usr/include/casacore/casa/OS/HostInfoIrix.h
/usr/include/casacore/casa/OS/HostInfoLinux.h
/usr/include/casacore/casa/OS/HostInfoOsf1.h
/usr/include/casacore/casa/OS/HostInfoSolaris.h
/usr/include/casacore/casa/OS/IBMConversion.h
/usr/include/casacore/casa/OS/IBMDataConversion.h
/usr/include/casacore/casa/OS/LECanonicalConversion.h
/usr/include/casacore/casa/OS/LECanonicalDataConversion.h
/usr/include/casacore/casa/OS/LittleEndianConversion.h
/usr/include/casacore/casa/OS/Memory.h
/usr/include/casacore/casa/OS/MemoryTrace.h
/usr/include/casacore/casa/OS/ModcompConversion.h
/usr/include/casacore/casa/OS/ModcompDataConversion.h
/usr/include/casacore/casa/OS/Mutex.h
/usr/include/casacore/casa/OS/Path.h
/usr/include/casacore/casa/OS/PrecTimer.h
/usr/include/casacore/casa/OS/RawDataConversion.h
/usr/include/casacore/casa/OS/RegularFile.h
/usr/include/casacore/casa/OS/SymLink.h
/usr/include/casacore/casa/OS/Time.h
/usr/include/casacore/casa/OS/Timer.h
/usr/include/casacore/casa/OS/VAXConversion.h
/usr/include/casacore/casa/OS/VAXDataConversion.h
/usr/include/casacore/casa/OS/malloc.h