eld seems to set e_flags to all 1s when --format=binary is used

**Reproducer**
```
cat > mydata.blob << '!'
asdf
!

ld.eld -melf32lriscv -r --format=binary mydata.blob -o mydata.elf

llvm-readelf --headers mydata.elf
#   Flags:                             0xFFFFFFFF, RVC, single-float ABI, double-float ABI, quad-float ABI, RVE, TSO
```

lld, bfd seem to set it as 0 here.