[Coco] Announcement : Nitros-9 C compiler tool cross chain for Linux

[Walter Zambotti]

I managed the get the full C tool chain working.

Here is the readme from the github site:

https://github.com/WallyZambotti/Nitros9-CC-CrossCompiler

Linux CC cross compiler for (CoCo) Nitros-9

It contains:

- cc2.5.3 : c front end
- cprep19 : c preprocessor
- c.comp : c compiler
- c.opt - (c) rma asm optimizer
- rma(r63) - relocating macro assembler
- rlink - linker
- ansifront - ANSI C to K&R preprocessor

It has been successfully compiled and tested on Ubuntu 18.04 (AMD).

All Linux binaries produced are 32bit.  Some binaries are required to be 
compiled with no optimization or they will fail.  Be warned if you change
the make files.

It is known to work on Intel (AMD) platforms.

This C compiler tools chain produces binaries compatible with:

  Nitros-9 (MC6809 or HD6309).

A test directory is provided that contains a dd directory.  You should place
the Linux executables in the dd/cmds directory and create a symbolic link from 
/dd to that directory:

  $ sudo ln -s ~/Nitros9-CC-CrossCompiler/test/dd /dd

And add the cmds directory to your path:

  $ PATH=$PATH:/dd/cmds

Some libraries and defs files are also provided under the test/dd/lib & test/dd/defs
directories.  You can add more by copying them from a Nitros-9 distribution.

You will then be able to compile Nitros-9 C programs with the same instructions
as normally used under Nitros-9:

  $ cc253 -A -s helloworld.c -f=helloworld
  $ cc253 main.c sub1.c sub2.r mylib.r -f=myprog
  
The provided example in the test directory can be compiled with:

  $ cc253 -A -s texturebm.c gfxlib.c gpulib.c -f=texturebm

(However this example program will only run on the OVCC emulator with the MPU
device installed in one of the MPI slots.)

When copying the executables to Nitros-9 (either real or emulator) for execution 
remember to set the execute attributes:

  $ attr myprogram e pe