I see. It is uncomon to see a single header being named a library. I am not familiar with it. I suspect you need to first compile that into a library, and then include that library in your source code. But maybe it is intended to work in a different way.
Well, how silly of me. But ofcourse you have to install it as root.
Although it seems like it might be installed in any directory of your choice, on my system it defaults to /opt.
I never gave this a thought, since I always install apps as root. So it did not occur to me to hint this as a solution
I'm glad you figured it out though.
The -I option for configure indeed works; sadly the mingw headers (Ubuntu 14.04 deb) explicitly fail compilation if the target isn't Win32 so rather than burn more time on this, I'll look at switching the offending tools to cross compile.
I'm far from certain what the expected target is for the Qt tools when cross compiling; should SDK bundled tools build for the host or target?
I am not a lawyer so for licensing issues you should either contact one or talk with Digia directly.
Yes, you'll only have a dependency on VS runtime but it's normal and it's better to keep it so.
This bug has been reported https://bugreports.qt-project.org/browse/QTBUG-39859
For now they found another workaround which doesn't involve changing any file: simply install libEGL-dev. (e.g with linux MINT the package libegl1-mesa-dev avoid the error).