PackageOverrides.txt is not parsed correctly

[ericstj]

See:

sdk/src/Tasks/Microsoft.NET.Build.Tasks/ResolveTargetingPackAssets.cs

Lines 146 to 151 in e2faeba

	private TaskItem CreatePackageOverride(string runtimeFrameworkName, string packageOverridesPath)
	{
	TaskItem packageOverride = new TaskItem(runtimeFrameworkName);
	packageOverride.SetMetadata("OverriddenPackages", File.ReadAllText(packageOverridesPath));
	return packageOverride;
	}

This reads the entire contents of the file and sets it as metadata.

This creates a problem, because the consumption of the PackageOverrides assumes delimited packages, and the task is not inserting delimiters.

See #2937 (comment)

To fix this the task should either insert the delimiters, or we should change the file to append a semi-colon after every package ID.

[ericstj]

/cc @dsplaisted @dagood

[dagood]

/cc @NikolaMilosavljevic FYI