During archive, we include section sizes as listed in the linker map file, but this includes sections that get stripped.
* Including the stripped sections adds noise, and inflates the size of symtab
* We should instead use readelf against the stripped binary.
  * We already collect this, so the change would just be to use it instead of the map file data.

Also: We should delete unpacked relocation sizes:
https://cs.chromium.org/chromium/src/tools/binary_size/libsupersize/archive.py?rcl=afeccd76584c3f1512453836484a1a88b2b9f12b&l=1049

This code hasn't worked since we switched to lld (the linker directly packs relocations). 
We should just delete the "(unpacked)" metrics.