postprocess: Support statically-linked ELF as input

Merge functionality from the nanoapp_genbinary tool into
nanoapp_postprocess, to support parsing data directly from an ELF file
and handling relocs generated by statically linked nanoapps.

Bug: 28870324
Change-Id: I61d636229a5a4f50135a196db8c9ea1cc5165e6e
3 files changed