fix the compile failed '/usr/bin/ld: cannot use executable file 'payload.o' as input to a link'

[purplewall1206]

gcc-ld version GNU ld (GNU Binutils) 2.36.1 link the 'payload.o' into an executable format.

But when make link the 'payload.o' and 'kvm-hello-world.o' , ld only accepts relocatable files as inputs.

To fix the compile failure, I add '-r' in the link command and make the output 'payload.o' relocatable format.