Fix mkfifo on Linux.
Fix mkfifo on Linux.

The build failed because of type mismatch errors for the mode
permission.

hexsel/coreutils,jbcrail/coreutils,silvio/rust-coreutils,beni55/coreutils,kwantam/coreutils,sshling/coreutils,kball/coreutils,bundai223/coreutils,Arcterus/coreutils,beni55/coreutils,kwantam/coreutils,sshling/coreutils,Heather/coreutils,Gianbaoluo/coreutils,dbrgn/coreutils,retep998/coreutils,efuquen/coreutils,Shir0kamii/coreutils,mauricio/coreutils,keunwoo/coreutils,Shtong/coreutils,hexsel/coreutils,retep998/coreutils,Shtong/coreutils,filmor/coreutils,filmor/coreutils,silvio/rust-coreutils,jbcrail/coreutils,tempbottle/coreutils,dennis/coreutils,uutils/coreutils,Heather/coreutils,wimh/coreutils,dennis/coreutils,bundai223/coreutils,samfoo/coreutils,samfoo/coreutils,uutils/coreutils,steveklabnik/coreutils,tempbottle/coreutils,kball/coreutils,Shir0kamii/coreutils,keunwoo/coreutils,steveklabnik/coreutils,Gianbaoluo/coreutils,kevgeniy/coreutils,efuquen/coreutils,dbrgn/coreutils,ebfe/coreutils,wimh/coreutils,uutils/coreutils,dbrgn/coreutils,ebfe/coreutils,kevgeniy/coreutils,Arcterus/coreutils,mauricio/coreutils