Multiple build issues

[tjayz]

qt.mk line 3 change to:
$(package)_download_path=https://download.qt.io/new_archive/qt/5.9/5.9.7/submodules/

zlib.mk line 3 change to:
$(package)_download_path=https://www.zlib.net/fossils/

At some point boost dl path had an issue for me and had to resort to changing line 3 boost.mk to:
$(package)_download_path=https://sourceforge.net/projects/boost/files/boost/1.70.0/

If compiling native in linux with qt enabled. per build-unix-deb.md line 29, those libraries will result in failed build. Need to build dependencies per /depends/readme.md and build with -DCMAKE_TOOLCHAIN_FILE=../cmake/platforms/Linux64.cmake.

To cross compile to windows, per build-windows.md lines 100/101, I had to build under win32 with ~10 failed builds till nothing new could be compiled via the win32 threads before switching to posix, wherein depending on the options selected, you may fail several times as well before succeeding with all the .exes.

Also, per build-windows.md line 138 I believe the following should be added:
-DBUILD_RADIANT_WALLET=ON -DBUILD_RADIANT_TX=ON -DBUILD_RADIANT_CLI=ON

I hope this information helps others.