Extra messages from Makefile.sphinx

[Jim Davis]

On a sphinx-free Ubuntu system with 4.10-rc5, make installmandocs
works just fine, but the garrulous Makefile.sphinx twice tells me I
don't have sphinx-build installed:

Documentation/Makefile.sphinx:22: The 'sphinx-build' command was not found. Make
 sure you have Sphinx installed and in PATH, or set the SPHINXBUILD
make variable to point to the full path of the 'sphinx-build'
executable.
  SKIP    Sphinx include/config/auto.conf target.
Documentation/Makefile.sphinx:22: The 'sphinx-build' command was not found. Make
 sure you have Sphinx installed and in PATH, or set the SPHINXBUILD
make variable to point to the full path of the 'sphinx-build'
executable.
  SKIP    Sphinx installmandocs target.

Would the 'SKIP ...' statements suffice?  It happens with make
cleandocs and make mandocs too.
-- 
Jim