Fixed make builddoc and others
Fixed make builddoc and others

Stopped 'make builddoc' and other targets from always rebuilding
even if nothing changed by fixing two issues in the Makefile:

- The pywbem_os_setup.bat/.sh scripts were both listed as dependents
  but only one was downloaded on each OS. Now, only the needed one
  is defined as dependent.

- The index.html file moved at some point (from build_doc/html/docs to
  build_doc/html) but the Makefile was not updated accordingly.

Signed-off-by: Andreas Maier <38dbb04957d222ea6ce72de72413b1e55e665472@de.ibm.com>

pywbem/pywbemtools,pywbem/pywbemtools