I wonder how long it takes to compile on an RPi. I tried it once with the full Qt build and gave up :) Of course, I should have cross-compiled but I guess I didn't want it enough.
Takes about 10 minutes to build on a 3 GHz i7-2600K. So maybe an hour or two on an RPi?
The impressive thing is that the build instructions are like 3 lines long, and actually result in a working build. No drama, no specific compiler versions required, no CMake or autotools or other external crap, no dependency hell... just lots of cl.exe invocations scrolling by, followed by a command prompt.
I just tried on a Raspberry Pi Model 3B, BCM2835 ARMv7, 4 cores, Raspbian Linux 4.9.59-v7+ armv7l; "time ./lua build.lua ../LeanQt -P HAVE_GUI" reported 65 minutes (rounded).
Compiling qt on the pi is an overnight sort of thing. I think it took 12+ hours when I did it on a pi4. Thankfully, once it's compiled, you don't have to compile again until you next version bump.
Compiling Qt with the right switches is hard enough, before you throw in cross compiling on top. Since you only need to compile a new Qt release once every few months, why optimize the process? Just kick it off and go to sleep. I don't modify core Qt libraries ever. If I was iterating on Qt itself, I would definitely figure out cross compiling. Anyways if you come up with such a working cross-compile recipe, you should post it some place.
I think people working on cross compilation are wasting their time. They are trying to fix it "properly", separating build time dependency and run time dependency, because host system can't run cross compiled target binary. The obvious solution (what Scratchbox2 does) is for host system to run cross compiled target binary, instead of trying to "fix" the build system.
