Fetching build-dep qt*-opensource-src for foreign arch fails

[henning.schuett@mailbox.org]

Package: qtdeclarative-opensource-src
Version: 5.15.2+dfsg-6

Dear Maintainers,

I am trying to build Qt5 on a current debian for a foreign architecture using multi-arch. But when fetching the necessary build dependencies I run into the following error:
root@61e383731765:~# dpkg --print-architecture
arm64
root@61e383731765:~# dpkg --print-foreign-architectures
amd64
root@61e383731765:~# apt-get build-dep -a amd64 qtdeclarative-opensource-src
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
builddeps:qtdeclarative-opensource-src:amd64 : Depends: qtbase5-doc-html:amd64 (>= 5.15.2+dfsg~) but it is not installable
E: Unable to correct problems, you have held broken packages.

It looks like the dependency is linked to qtbase5-doc-html:amd64 which is not available as it is architecture independent.

I tried some other packages and qtsvg-opensource-src, qtmultimedia-opensource-src, and qt3d-opensource-src seem to have similar issues. While qtbase-opensource-src works as I would expect it.

I tried to fix it myself in the debian/control files. It seems that qtbase5-doc-html is a build-depends-indep and only removing the line completely and installing the dependency manually really seemed to resolve the error for me.

I also tried the other way around using a amd64 machine and install build-dep for arm64 but that resulted in the same erros.

Am I doing something wrong or is this a bug?

Thanks,
Henning