Fix plugin loader (#2052)

[berolinux]

The lxqt-plugin binary needs to export symbols that should be visible to plugins being loaded with QPluginLoader or dlopen.

Fixes #2052

[yan12125]

Thanks for the fix, I can confirm it works. Just an issue: https://cmake.org/cmake/help/latest/variable/CMAKE_EXECUTABLE_ENABLE_EXPORTS.html says CMAKE_EXECUTABLE_ENABLE_EXPORTS is added in CMake 3.27. I'm not sure if it's too new for Linux/BSD/... distributions.

[stefonarch]

Indeed it's on the edge:
https://repology.org/project/cmake/versions

[luis-pereira]

CMAKE_EXECUTABLE_ENABLE_EXPORTS was introduces in version 3.27 released in Jul 2023. Too recent IMO.

We can use the ENABLE_EXPORTS property:

set_property(TARGET ${PROJECT} PROPERTY ENABLE_EXPORTS TRUE)

It fixes the problem and it's available in the CMake versions we support.

[tsujan]

This may deserve a point release. Please decide what should be done. @luis-pereira, @yan12125?

[yan12125]

We can use the ENABLE_EXPORTS property:

This approach looks good (not tested yet)

[luis-pereira]

This approach looks good (not tested yet)

Pls test. It worked on my test.

[luis-pereira]

This may deserve a point release. Please decide what should be done. @luis-pereira, @yan12125?

If ENABLE_EXPORTS is found to work, we should use it, IMO.
It deserves a point release, IMO.

[Chiitoo]

This approach looks good (not tested yet)

Pls test. It worked on my test.

For what it is worth, worked for me.

Thank you!

[tsujan]

@luis-pereira
Would you please make a PR?

[luis-pereira]

@tsujan Done here
@berolinux Thanks for your work.

[yan12125]

Superseded by #2061