Install Plan9port on Linux

note, May 12, 2023 on Mitja Felicijan's blog

Install Plan9port on Linux. This applies to @@ -9,21 +9,18 @@ programs to Unix-like operating systems. Useful for programs like 9termgit clone https://github.com/9fans/plan9port $HOME/plan9 cd $HOME/plan9/plan9port ./INSTALL -r $HOME/plan9 -