Incremental sysimage build doesn't support packages with same name but different uuid

[krynju]

This one is similiar to #767, but setup and place where it errors are different.

Setup

Simple two projects that have a top level dependency PackageA, but with different uuids

using PackageCompiler

using Pkg

Pkg.activate("project1") # has Package1 with uuid=1234
create_sysimage(["Package1"]; sysimage_path="sysimage5.so")

Pkg.activate("project2") # has Package1 with uuid=5678
create_sysimage(["Package1"]; sysimage_path="sysimage6.so", base_sysimage="sysimage5.so")

Error

julia> create_sysimage(["Package1"]; sysimage_path="sysimage6.so", base_sysimage="sysimage5.so")
⠙ [00m:07s] PackageCompiler: compiling incremental system imageLoadError
⡆ [00m:08s] PackageCompiler: compiling incremental system imageimporting Package1 into Main conflicts with an existing identifier
in expression starting at /tmp/jl_bOn2oN:7
✖ [00m:08s] PackageCompiler: compiling incremental system image
ERROR: failed process: Process(`/home/krynju/julia-1.7.3/bin/julia --color=yes --startup-file=no --cpu-target=native -O3 --sysimage=sysimage5.so --project=/home/krynju/sameuuidtest/project2 --output-o=/tmp/jl_sKRDQC.o /tmp/jl_bOn2oN`, ProcessExited(1)) [1]

Error appears due to this code: https://github.com/JuliaLang/PackageCompiler.jl/blob/05f6854fb9147bd0faae7b442555cddc69457f64/src/PackageCompiler.jl#L377-L382

Solution

I worked around this by commenting out this part of code and everything looks to be functioning just right.

The error didn't appear if the package was the same uuid, but a different version, which is probably something weird to handle as well

A build flag to turn off this import behavior would probably be good enough as I'm not sure what the import to Main is dedicated for