qt5/qtwebchannel.nix: omit $bin output if cross

[ghost]

Description of changes

QtWebChannel does not produce binaries when it is cross-compiled. Let's omit the $bin output in that case.

[Artturin]

there's no binaries in $bin even when not cross-compiling

so these files aren't created when cross-compiling

$ tree ./result-bin
./result-bin
└── lib
    └── qt-5.15.8
        └── qml
            └── QtWebChannel
                ├── libdeclarative_webchannel.so
                ├── plugins.qmltypes
                └── qmldir

[ghost]

Let me clarify: QtWebChannel does not produce anything at all in $bin when cross-compiling.

This causes Nix to reject the build because the builder failed to create an expected output.

[Artturin]

Let me clarify: QtWebChannel does not produce anything at all in $bin when cross-compiling.

i understood that but why are qml files not generated when cross-compiling

plugins.qmltypes has this comment

// This file was auto-generated by:
// 'qmlplugindump -nonrelocatable -dependencies dependencies.json QtWebChannel 1.15'

qmlplugindump is in qtdeclarative which is in qtInputs which is propagatedBuildInputs in qtModule so the issue may be fixed by adding qtdeclarative to nativeBuildInputs

[SuperSandro2000]

If there are no files in $out/bin why do we even have the bin output? The files seem to be wrong there in the first place.

[ghost]

I will investigate.

It might be a week or two before I have time to return to this qt5-cross stuff, but I will get to it. Native-compiling stuff on my laptop is too painful.