Pkg.test is broken for stdlibs not in sysimage since 1.3

[KristofferC]

https://github.com/JuliaCI/NanosoldierReports/blob/master/pkgeval/by_date/2020-12/01/report.md

Just taking one of them:

     Testing Running tests...
ERROR: LoadError: ArgumentError: Package MbedTLS_jll [c8ffd9c3-330d-5841-b78e-0817d7145fa1] is required but does not seem to be installed:
 - Run `Pkg.instantiate()` to install all recorded dependencies.

Stacktrace:
 [1] _require(pkg::Base.PkgId)
   @ Base ./loading.jl:985
 [2] require(uuidkey::Base.PkgId)
   @ Base ./loading.jl:909
 [3] require(into::Module, mod::Symbol)
   @ Base ./loading.jl:896
 [4] include
   @ ./Base.jl:386 [inlined]
 [5] include_package_for_output(pkg::Base.PkgId, input::String, depot_path::Vector{String}, dl_load_path::Vector{String}, load_path::Vector{String}, concrete_deps::Vector{Pair{Base.PkgId, UInt64}}, source::String)
   @ Base ./loading.jl:1208
 [6] top-level scope
   @ none:1
 [7] eval
   @ ./boot.jl:360 [inlined]
 [8] eval(x::Expr)
   @ Base.MainInclude ./client.jl:446
 [9] top-level scope
   @ none:1
in expression starting at /home/pkgeval/.julia/packages/MbedTLS/4YY6E/src/MbedTLS.jl:1

[KristofferC]

This kinda looks like a Pkg regression from 1.3 to me...

It used to put path entries to the stdlibs in the test manifest but that seems to not be the case anymore. Probably related to the "sandbox" stuff that was added to Pkg...