[Xamarin.Android.Build.Tasks] fix the NuGetizer 3000

[jonathanpeppers]

Fixes: http://work.azdo.io/917139
Context: https://github.com/NuGet/Home/wiki/NuGetizer-Core-Features

The NuGetizer 3000, was failing on Xamarin.Android 9.4 with:

The "FilterAssemblies" task was not given a value for the required parameter "DesignTimeBuild".

This tool runs a GetPackageContents MSBuild target that is defined
here:

https://github.com/NuGet/NuGet.Build.Packaging/blob/dev/src/Build/NuGet.Build.Packaging.Tasks/NuGet.Build.Packaging.targets#L201

Since this isn't a Build or a Compile, neither of these targets
will run:

• _SetupDesignTimeBuildForBuild
• _SetupDesignTimeBuildForCompile

I don't think we can make the _AddAndroidCustomMetaData MSBuild
target (that runs <FilterAssemblies/>) depend on either of these.

The simple fix is to just remove [Required] from the
DesignTimeBuild property, as it will be fine for it to default to
false.

/cc @mrward @kzu

[mrward]

Thanks 👍

[jalbertSyncroTech]

Any updates on a release of this fix? We're in the process of evaluating VS2019 16.2 coming from 16.1.3, but our Release builds which generate NuGet packages are failing with this error message.

[jonathanpeppers]

@jalbertSyncroTech you didn't mention how you are running your build, but you can workaround by setting the MSBuild property:

msbuild foo.csproj /p:DesignTimeBuild=False

You can also try setting it in your csproj file if you are using the IDE.

[jalbertSyncroTech]

Thanks @jonathanpeppers! Explicitly setting DesignTimeBuild to false resolved the error message, I was able to add this to a .targets file that's we reference from every .csproj in our solution that does NuGet packaging. For reference, we use VS2019 both for TFS continuous integration builds and for developer IDE builds.

I'd expect that any Xamarin.Android users who create NuGet packages may run into this, so you may want to add a comment to the VS2019 16.2 Release Notes.