[PATCH] ld: add --package-metadata

[Florian Weimer]

* Fangrui Song:

> Both the "FDO" and the json dependency make me concerned -
> if a linker script approach works quite well, why bother with a new
> linker option with a very specific application?

The linker script does not work all that well because it requires that
the script is materialized to disk somewhere, and that path needs to
show up in the build flags.  If the build flags are stored beyond the
build for future use, this makes them invalid because the path will
typically be gone by the time the stored flags are used.

Thanks,
Florian