Add Custom Runtime Pack option

[naricc]

This adds an option to specify a custom runtime pack (currently only used by wasm, but in principle useful for other net5.0 appolications). This is used to run against a custom built net5.0 runtime.

[naricc]

@adamsitnik (I can't actually add reviewers)

[SamMonoRT]

@adamsitnik - is it possible to kick off a re-run of the BenchmarkDotNet - macOS lane to confirm it is not related to changes here. Also, if you have a moment, please review and merge if things look good. Thank you

[adamsitnik]

macOS lane to confirm it is not related to changes here

done

[adamsitnik]

LGTM, thank you @naricc !

Before I hit the merge button, could you please provide some simple example of benefits of this feature? I am not familiar with this concept (yet)

[naricc]

@adamsitnik So, the benefit is primarily if you want to make a change to the runtime (whether that is mono, or clr, or whatever) and measure some benchmark results against that change. It's very easy to make the changes to the runtime and produce a new runtime pack.

With out this option it's very hard to make changes to the runtime and actually have the benchmarks use the changed version. You could in principle package the changed runtime into a dotnet host that uses the runtime you just built, but it's not a simple process.

[naricc]

@adamsitnik

Or, to put it another way, runtime packs are how we can point a project at a specific runtime with out going through the laborious process of packaging that runtime into a dotnet host.

[adamsitnik]

runtime packs are how we can point a project at a specific runtime with out going through the laborious process of packaging that runtime into a dotnet host.

this is what I needed, thanks!

[adamsitnik]

@naricc this build should produce 0.12.1.1402 package within 30-40 mintues

[SamMonoRT]

Thank you @naricc and @adamsitnik for getting this in. Getting regular perf numbers will go a long way in improving what we ship to customers.