[rtems-source-builder] Python Virtual Env and MacOS arm64

[chrisj at rtems.org]

Hi,

These patches provide:

- GDB Python Virtual Env support

  If you start a build in a python virtual env it will be used as the
  path to python provided to GDB if GDB is version 13.* and later. Using
  a virtual env simplifes the support we need to maintain and in time
  this will become a requirement.

  GDB 13 requires Python 3 and so this means we are requiring users
  to move to Python 3. Python 2 and 3 support will remain in the RSB as
  we have planned until RTEMS 6 is released.

- MacOS M series support

  Support for M series is now stable. This work builds on the work
  Karel has done previously (thanks). There was a crash in xgcc when
  building the runtime libraires and it has been revolved with a configure 
  option to the GMP package.

  I have tested with Xcode 14.3 (14E222b) and MacOS 13.3.

  The GDB python virtual env support lets the python.org universal
  package installer be used. The ticket #4892 has the details.

  The need for a special configure option means the GMP package built
  and staged as part of the build set needs to be used so the internal
  GCC build of GMP has been removed. GMP is built as a package for
  GDB.

  I think in time we will move away from the GCC internally built
  packages to separate packages so we can provide the fine grain
  control we seem to need.

  MPFR has been updated to 4.2.0 for MacOS support. This is fetched
  from the MPFR home site.

  Microblaze's GCC does not build as the version does not recognize
  the machine `arm64-apple`.

  SH does not build on MacOS and I am not sure if this is happening
  on all hosts or just MacOS.

- DCT warnings

  These are now disabled as DTC had warnings with Xcode. I prefer
  we disable warnings or errors from warnings because newer compilers
  may generate new warnings and that breaks releases years later.

- MIPS STX GDB

  This failed to build GDB 13.1 because GMP is needed and the build
  set was not a separate staged build. This has been corrected and
  the config files have been cleaned up.
 
I have tested all buildable packages on MacOS arm64 and some on
FreeBSD and PowerPC on Linux Rocky.

Chris