Let's do the iOS specific stuff in separate main() source
file(s). Don't attempt to build complete iOS programs using normal
LibreOffice mechanisms, it will work for only the very lowest level
unit tests anyway, because of static linking and the circularish
UNO/URE/bootstrap/whatnot (run-time) dependencies between different
parts of the code.

We thus can't build the various iOS-specific *_cppunittester_all unit
test executables any more. Corresponding unit tests (and more complex
ones) for iOS will have to be done in a different way.

as opposed to crashing

1. rename the tool to lodownloadtest.py
2. it will call native losmoketest in lo program directory
3. it will download test package as well as lo installables
4. fixing some bugs and optimize code
    - clean up extracted rpms after install
    - only uninstall necessary packages before installation
    - trivial improvements please see diff

so pesky warnings about invalid property values on shutdown go away

Rather check iterator validity *before* accessing it. valgrind
warning on linux, and crash on windows for e.g. doc at n#736495.