[FATAL] Error in invoking target 'irman ioracle...' of makefile 'ORACLE_HOME/rdbms/lib/ins_rdbms.mk'. See 'ORA_INVENTORY/logs/InstallActions.../installActions....log' for details

This error occurred during installation of new Oracle RU to new oracle home. The linking phase was going on. The out-of-memory operating system protection mechanism had killed the linking process. 

The main cause of it had been vm.swappiness=0 settings (had been set in sysctl.conf before); in other words, operating system was disabling any swap activity if it could do so. Any values more that 0 resolved the issue (by repeating the installation).