[ELF] -r: don't create .interp

`{clang,gcc} -nostdlib -r a.c` passes --dynamic-linker to the linker,
and the expected behavior is to ignore it.

If .interp is kept in the relocatable object file, a final link will get
PT_INTERP even if --dynamic-linker is not specified. glibc ld.so expects
to see PT_DYNAMIC and the executable will likely fail to run.

Ignore --dynamic-linker in -r mode as well as -shared.