[BOLT][DWARF] Force allocation of debug_line in RuntimeDyld

Summary:
Currently, RuntimeDyld will not allocate a section without relocations
even if such a section is marked allocatable and defines symbols.

When we emit .debug_line for compile units with unchanged code, we
output original (input) data, without relocations. If all units are
emitted in this way, we will have no relocations in the emitted
.debug_line. RuntimeDyld will not allocate the section and as a result
we will write an empty .debug_line section.

To workaround the issue, always emit a relocation of RELOC_NONE type
when emitting raw contents to debug_line.

(cherry picked from FBD32909869)