Enabling CMAKE_INTERPROCEDURAL_OPTIMIZATION (LTO) causes executables to be linked twice

[equeim]

Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a bug that matches the one I want to file, without success.

flatpak-builder version

1.4.4

Flatpak version

1.15.12

How to reproduce

1. Build example from test.zip

Expected Behavior

test executable is linked once.

Actual Behavior

test executable is linked twice, first at build step and then at install step.

Additional Information

Minimal example: test.zip

This happens both with "buildsystem": "cmake" and "buildsystem": "cmake-ninja". It does not happen when running build && install on the host, without flatpak-builder.