scons unhappy if tar not installed

[Hal Murray]

It builds and checks on various OSs/distros/hardware.

I'm only building the core. Mostly because I haven't installed the 
prerequisites.


WARNING: Some documentation and html will not be built.
AttributeError: 'SConsEnvironment' object has no attribute 'Tar':
  File "/home/murray/gpsd/raw/SConstruct", line 63:
    SConscript('SConscript',
  File "/usr/lib/python3.9/site-packages/SCons/Script/SConscript.py", line 661:
    return method(*args, **kw)
  File "/usr/lib/python3.9/site-packages/SCons/Script/SConscript.py", line 598:
    return _SConscript(self.fs, *files, **subst_kw)
  File "/usr/lib/python3.9/site-packages/SCons/Script/SConscript.py", line 287:
    exec(compile(scriptdata, scriptname, 'exec'), call_stack[-1].globals)
  File "/home/murray/gpsd/raw/gpsd-3.21.1~dev/SConscript", line 3176:
    targz = gzenv.Tar(target + '.gz', distfiles)
WARNING: asciidoctor not found.
WARNING: Some documentation and html will not be built.


-- 
These are my opinions.  I hate spam.