Qt5 i386 build problem on Launchpad

I'm the author of LinSSID, and I'm trying to build the next version, 2.3, on Launchpad. The amd64 build goes perfectly. The i386 version fails. The cause of the failure, according to the build log, is the build script looking to execute qmake from /usr/lib/x86_64-linux-gnu/qt5/bin/ instead of from /usr/lib/i386-linux-gnu/qt5/bin/ .

Here's where it gets strange. First, the *exact* build structure worked perfectly a month ago when I built version 2.2. The build files for qmake (.pro, .pri) were not touched. Only a bit of c++ source was changed. Stranger still, when I run the build for i386 on a local pbuilder environment it works perfectly. It only fails buillding i386 on Launchpad.

From the build log, it seems the build script executes the first qmake call, on the top level .pro file, using the i386 path. That file sends the script to a sub-directory with another .pro file which is, again, called with qmake from the i386 path. When that file sends the script to a third-level subdirectory with a .pro file, it tries to execute qmake from the x86_64 path instead of the i386 path – and there it dies.

Why the build script is looking in the x86_64 path at that point is the mystery. It's like something somewhere changed the PATH environment variable in the chroot environment. I've looked all through the code and I can't find anything that would do that. And, again, it's the same build code that ran just fine a month ago.

I tried another version, including qtchooser in the build dependencies but it had no effect.

The build log is here: https://launchpad.net/~wseverin/+archive/ppa/+build/6160008/+files/buildlog_ubuntu-trusty-i386.linssid_2.3-2_FAILEDTOBUILD.txt.gz

I've already shot a whole day on this and I'm no closer to a solution. Any help will be greatly appreciated.

Thanks,
-Warren