This issue was fixed with the simultaneous release of libopenshot-0.2.3 and libopenshot-audio-0.1.8 on 2019-03-22. The new releases use an upgraded and streamlined build of the Juce library sources, removing the problematic modules which were causing FTBFS issues with GCC 9. See upstream issue https://github.com/OpenShot/libopenshot-audio/issues/33 .
libopenshot-audio-0.1.8 release: https://github.com/OpenShot/libopenshot-audio/releases/tag/v0.1.8 libopenshot-0.2.3 release: https://github.com/OpenShot/libopenshot/releases/tag/v0.2.3 (The OpenShot application also released version 2.4.4 at that time: https://github.com/OpenShot/openshot-qt/releases/tag/v2.4.4 )
