bisecting revealed since introduction of this line

i.e. objdump -p ./dist.x86_64-pc-linux-gnu/lib/libgrass_imagery.8.0.so | grep SONAME should not be empty but something like SONAME libgrass_imagery.8.0.so

this missing SONAME leads to

• downstream issues like [RPM] Backport a downstream spec fix for GRASS' libgrass_imagery qgis/QGIS#47576 and
• workarounds https://src.fedoraproject.org/rpms/qgis/c/115e2008ceee0ebcba88dcbe8580eca514f6f08d?branch=rawhide

thanks for reworking this Makefile 😄