New Plan 9 user here from the SDF bootcamp! I'm trying to follow a basic hello world tutorial on http://sdf.org/?tutorials/Plan_9_C but I'm running into issues with compiling and linking with 8c and 8l. What is causing a "exec header invalid" on such a basic program? I have the commands that I typed in the screenshot.

Switching to 6c and 6l doesn't seem to work either I'm getting when I run 6l: ??none??: cannot open file: /amd64/lib/libc.a