building SLEPc with gcc-10
Judging by the report at https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=966981 , gcc-10 isn't quite happy with the fortran arguments used in bv test1f.F90
It looks like the Argument mismatch issue listed at https://gcc.gnu.org/gcc-10/porting_to.html
Likely it will build fine if -fallow-argument-mismatch (or -std=legacy) is used with gfortran, but a perhaps an update to the code might be preferable.