[Development] Source build woes on windows

[Kuba Ober]

I'm trying to build 5.1.1 from source (.zip download) on Windows using MSVC2012, in a separate
prefix (shadow) build. So far I've run into two issues:

1. configure.bat fails to bootstrap without .gitignore being present. Wouldn't it be better to check for
presence of configure.exe? Are we only supposed to build from a git clone? If so, is there any purpose for
the .zip/.tar.gz downloads? The workaround is to manually add .gitignore. Or else I'm just very confused :(

2. Having configured with -qt-zlib, prefix/qtbase/include/QtZlib is missing. In other words, the zlib headers
are not copied over from the source to the build prefix. This makes the qtsvg build fail. I've looked for
a file that has a list of headers to copy over during qtbase build, but couldn't find it. Any pointers? I'd like
to add QtZlib there and see if it would succeed. https://bugreports.qt-project.org/browse/QTBUG-32641 seems
related, but without QtZlib even being in $$[QT_INSTALL_HEADERS/get], it won't work.

Thanks, Kuba