bump Pkg to latest set of 1.6 backports

[KristofferC]

Fixes #38654

[KristofferC]

Trying a few of the packages that started failing.

@nanosoldier runtests(["AutoGrad", "MbedTLS", "NBodySimulator"], vs = ":master")

[nanosoldier]

Something went wrong when running your job:

NanosoldierError: failed to run tests: Build for julia on x86_64-linux-gnu did not complete successfully

Logs and partial data can be found here
cc @maleadt

[KristofferC]

I don't understand exactly how, but I guess

Error in testset Tar:
Test Failed at C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\stdlib\v1.6\Tar\test\runtests.jl:85
  Expression: Tar.tree_hash(tar, skip_empty = true) == hash
   Evaluated: "76b0aa58fdf559bada99754472f09838909ec4e7" == "b64eef11d100f2ccf9435f78be5459bbaabcabe6"
Error in testset Tar:
Test Failed at C:\buildbot\worker-tabularasa\tester_win64\build\share\julia\stdlib\v1.6\Tar\test\runtests.jl:85
  Expression: Tar.tree_hash(tar, skip_empty = true) == hash
   Evaluated: "76b0aa58fdf559bada99754472f09838909ec4e7" == "b64eef11d100f2ccf9435f78be5459bbaabcabe6"
...

on Windows is related to JuliaLang/Pkg.jl#2253?

cc @StefanKarpinski, @staticfloat

Edit: I guess https://github.com/JuliaIO/Tar.jl/blob/77c0db7d17a86852b3eaa94176db968f4cbfabed/test/setup.jl#L19 would do it.

[maleadt]

PkgEval doesn't work on Julia master right now: #38680

[StefanKarpinski]

I don't entirely understand what's happening there: @staticfloat, you changed the behavior of GitTools.tree_hash, right? It should be more correct now. This looks like that fix introduced a discrepancy with Tar.tree_hash that wasn't there previously.

[KristofferC]

That's my understanding as well.

[staticfloat]

I'm trying to reproduce this, but so far haven't been able to.

[staticfloat]

I figured it out; Stefan is going to fix Tar to fix that.