Apps/libraries/sysimages that have no package dependancies trigger unnecessary warning

[LilithHafner]

If I make a simple package with no dependencies and compile it to a sysimage/app/library with PackageCompiler, I get:

┌ Warning: it is not recommended to create an app/library without a preexisting manifest
└ @ PackageCompiler ~/.julia/packages/PackageCompiler/X7R0D/src/PackageCompiler.jl:66

Even though I do have a preexisting manifest file, it's just empty:

# This file is machine-generated - editing it directly is not advised

julia_version = "1.7.3"
manifest_format = "2.0"

[deps]

This is because a manifest without dependencies is interpreted as a missing manifest.

PackageCompiler.jl/src/PackageCompiler.jl

Line 65 in a8a4459

if isempty(ctx.env.manifest)

(from discourse)

[DilumAluthge]

I believe this is closed by the combination of #705 and #715?