Add generic RTEMS tar file system support

[skliper]

Is your feature request related to a problem? Please describe.
Current PC RTEMS workflow creates a fat32 disk image and QEMU command line drive option for runtime access. See:
https://github.com/nasa/cFS/blob/main/.github/scripts/rtems-test.mk

Flight systems often utilize flat nonvol memory for boot/startup which can be done using RTEMS support for linking a tared filesystem with the executable and populating the root file system from the tar file at startup.

Describe the solution you'd like
Add generic support for RTEMS tar filesystem

Describe alternatives you've considered
EEFS is an alternative simple file system, adding RTEMS tar filesystem support doesn't preclude using other options.

Additional context
None

Requester Info
Jacob Hageman - NASA/GSFC

[DavidEdell]

How do you utilize this new TARFS support?

I can enable it by setting RTEMS_INCLUDE_TARFS, however that results in a link error because the tar file itself is not generated and linked in. I don't see anything committed that would generate the tar file.
Is there another piece that has not been pushed/merged?

I'm ultimately looking at getting the latest cfe version running on one of our Leon3 boards.

thanks,
-David

[skliper]

We are using it on a Leon3. Along with nasa/PSP#376, we added a "tarfs" target to do the last stage. So the process is to build for the leon3 with the following critical settings:

set(RTEMS_DYNAMIC_LOAD      TRUE)
set(RTEMS_INCLUDE_TARFS     TRUE)

Then we just do a cmake TARGET=tarfs prep. It's kludgy at this point since we just needed something that worked for us, but see nasa/cFE@main...skliper:cFE:EXAMPLE-tarfs. Note I just threw this into the cFE sample_defs to share, it relies on gaisler tools, etc so it won't just work out of the box.