Pass Custom Build Parameters

There are lots of times I find myself wanting to pass custom build parameters to the projects BenchmarkDotnet generates, but there is currently no way to do this.

This feature would be useful for debugging, if you want to, for example, have CI machines produce binlogs of the build. But it is also useful for testing the performance of different build options.

I think it can be done by generalizing the mechanisim used here with some command line options: https://github.com/dotnet/performance/blob/686f552943ccef56e8404ed0a060fcc1e689a2a0/src/harness/BenchmarkDotNet.Extensions/RecommendedConfig.cs#L40