[Development] Qt 6 buildsystem support requirements

[Oswald Buddenhagen]

On Wed, Aug 01, 2018 at 09:01:40AM +0000, Edward Welbourne wrote:
> Jason Newton (1 August 2018 10:24)
> > One of the things I like about the way bazel keeps this is I can jump
> > back and forth between an optimized build and a full debug build (for
> > example) - they don't erase eachother
> 
> This is easy to do in any build system that supports out-of-source
> (a.k.a. "shadow") builds - notably including the existing qmake-based
> builds for Qt.  I never want to do an in-source build of anything.
> 
indeed, that's why the example was badly chosen.

> > and you can only achieve that jumping capability, being cheap, if you
> > add a file-level layer of indirection.
> 
> Not sure what you're claiming here, or what system you're claiming lacks
> it.  If you've got both optimised and debug builds, you're going to have
> both sets of files *somewhere* (whether jumbled up in one directory or
> kept separate in two out-of-source build trees).
> 
but having fully separate trees for only mildly different builds is
wasteful. a smart developer addresses that by having ccache in the
background, but the solution is more efficient and comprehensive when
the build tool itself implements it.
hence https://bugreports.qt.io/browse/QBS-57