python, python2, python3 and gdb

[Chris Johns]

Hello,

This is all a bit messy. The ticket ...

 https://devel.rtems.org/ticket/3537

... is about upstream python removing the 'python' command. I have created a
patch ...

 https://lists.rtems.org/pipermail/devel/2018-October/023281.html

... that shows a way we can manage the problem for our tools that are built
using python. We need this type of solution because I think we will have users
with a mix of python, python2 and python3 on systems for years to come.

There are some complications. The first is GDB. We currently use
'--enable-python' with gdb however this has the side effect of letting gdb
select the python version and so the python libraries it links too. It is only
recently support for python3 has been added so older releases as found on 4.11
only support python2. Second Windows can have 3 different builds of python, an
MSC build python users can install, an MSYS build which is like a cygwin build
and finally a MinGW build and each can be python2 or python3. The RSB Windows
host support restricts the type of python being run to MinGW because these are
the only libraries a MinGW gdb can link with.

I will investigate if gdb can accept a library path and if it does a way to find
the libraries will be needed. If we then move the gdb build in the tools build
set to first it would help the long standing issue of a build failing at the end
with python.

I will add tickets to the 4.11 and 4.10 branch and any solution we decide on
will need to be added to those branches.

Chris