GH2953: Allow setting MSBuild target via MSBuildSettings using a string

[sbwaggoner]

PR to address this feature request:

#2953

[dnfadmin]

All CLA requirements met.

[sbwaggoner]

Is there something else I need to do to move this forward? It's my first contribution and I don't want to miss anything.

[augustoproiete]

Thanks @sbwaggoner. You're all set. Next step is for us to review and merge or give you feedback when we have chance.

[devlead]

I would expect something like this

Suggested change

	foreach (var target in value.Split(";").Where(p => !string.IsNullOrEmpty(p)))
	Targets.Clear();
	foreach (var target in value?.Split(';', _targetStringSplitOptions) ?? Array.Empty<string>())

so setting Target to a new value isn't keeping the old values or what do you think @augustoproiete ?

Where is something like this on top of class

#if NETCOREAPP3_1
        private static readonly StringSplitOptions _targetStringSplitOptions = StringSplitOptions.RemoveEmptyEntries;
#else
        private static readonly StringSplitOptions _targetStringSplitOptions = StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries;
#endif

[FrankRay78]

Hello @devlead, I have merged changes from sbwaggoner:feature-addition-target-initializer-msbuildsettings (which are now many commits behind) onto a local, up-to-date develop branch and intend to consider your review comments above. I've been looking for a way to contribute, perhaps this will be a good first issue for me to help get over the line.

[devlead]

Superceeded by #3954