[dev.link] cmd/link: convert second phase of DWARF-gen to use loader
This converts the second portion of DWARF-gen (dwarfGenerateDebugSyms
function and friends) to use the loader, as opposed to sym.Symbols.
Second phase is invoked as part of dodata(), which is fairly far along
in the linker, meaning that the "converted to loader.Symbol" wavefront
has not yet reached that point.
To account for this, the patch contains some shim code that runs
initially to copy back things from sym.Symbols into the loader
(notable symbol values), and then a second hook to be code after
dwarf-gen is complete to that copies the results back into the
appropriate sym.Symbols. This code is obviously temporary, but needed
for the time being.
Change-Id: I9b830b08b16480a1a5230cb52b592db1c550af18
Reviewed-on: https://go-review.googlesource.com/c/go/+/220987
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com> Reviewed-by: Jeremy Faller <jeremy@golang.org>