component/slapos: fix the OBS compilation

We need LD_LIBRARY_PATH only during OBS compilation (since the rpath is
not correctly set during compilation because it already points to final
/opt/slapos path).

This is a fixup of 61c13f54.
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passed Cloudooo.UnitTest-Master

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3Next

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failed SlapOS.KVM.ResilienceTest-Master

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failed SlapOS.SoftwareReleases.IntegrationTest-Master

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passed SlapOS.Theia.ResilienceTest-Master-ERP5

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passed SlapOS.Theia.ResilienceTest-Master-Gitlab

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failed Zodbtools.UnitTest-Master.ZODB6.Python3

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