AOT test failure in Julia 1.6-DEV (upstream issues)

### Issue (1) `--project` does not work with `--output-o`

> ```
> [ Info: PackageCompiler: creating system image object file, this might take a while...
> ERROR: ArgumentError: Package PyCall not found in current path:
> - Run `import Pkg; Pkg.add("PyCall")` to install the PyCall package.
> ```
>
> --- https://travis-ci.org/github/JuliaPy/PyCall.jl/jobs/722001094#L738

I think this is an upstream issue: https://github.com/JuliaLang/julia/issues/37441

I think this failure is observable only if you don't have PyCall in the default environment.

### Issue (2) A breaking change in `Pkg.Artifacts.@artifact_str`

https://github.com/JuliaLang/PackageCompiler.jl/pull/443

### Issue (3) "undefined symbol" error

https://github.com/JuliaLang/PackageCompiler.jl/issues/445

Start with the AOT failure output and the linked Julia issue 37441 and PackageCompiler reports 443 and 445. Reproduce the test under Julia 1.6-DEV without PyCall in the default environment, then compare the three failures with current upstream behavior. Done means each failure is confirmed as an upstream blocker or reduced to an actionable PyCall change.

Scritto dal modello di indicizzazione a partire dal testo della issue.