QMAKE_HOST.arch being passed to GN causes build failure in 32 bit environment on 64 bit host

I'm running an AMD64 host with a 32 bit only chroot, in which I want to build Qt including QtWebEngine for an ARM target. Setting GN_HOST_CPU in qtwebengine/src/core/config/linux.pri to $$QMAKE_HOST.arch causes GN to add "-m64" to the compile flags, even if the current toolchain does not support this.

I see 2 ways out of this: explicitely testing if compiling, linking and running a hello world using "-m64" actually works, or simply passing whatever qmake was used to compile with (i.e. it was build as 32 bit binary -> x86).

For the meantime I run the entire changeroot using the linux32 personality, which leads to

host_cpu="unknown"

instead of

host_cpu="x64"

being passed (and everything working fine).