Commit 3c18e436cd makes it impossible to
build LMMS with embedded ZynAddSubFX if "-Wl,--as-needed" is used in
LINKER_FLAGS during the link step of RemoteZynAddSubFx:
Linking CXX executable RemoteZynAddSubFx
libZynAddSubFxCore.so: undefined reference to `fftwf_plan_r2r_1d'
libZynAddSubFxCore.so: undefined reference to `fftwf_execute'
libZynAddSubFxCore.so: undefined reference to `fftwf_destroy_plan'
This happens because fftw3f, which is a system lib, is linked to before
the ZASF core libs when linking RemoteZynAddSubFx. With "--as-needed",
correct library order matters.
(cherry picked from commit 0f28295ac7)