add `--justBuild` for users who want to reuse code produced by BDN without running the benchmarks

[adamsitnik]

Sample:

dotnet run -c Release -f net5.0 --filter *Basic* --justBuild true

// start dotnet  build -c Release --no-restore /p:UseSharedCompilation=false /p:BuildInParallel=false /m:1 /p:Deterministic=true /p:Optimize=true in D:\projects\BenchmarkDotNet\samples\BenchmarkDotNet.Samples\bin\Release\net5.0\DefaultJob
Microsoft (R) Build Engine version 17.2.0-preview-22104-01+09bdfae16 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.
  You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  BenchmarkDotNet.Disassembler.x64 -> D:\projects\BenchmarkDotNet\src\BenchmarkDotNet\Disassemblers\net461\win7-x64\BenchmarkDotNet.Disassembler.x64.exe
  BenchmarkDotNet.Disassembler.x86 -> D:\projects\BenchmarkDotNet\src\BenchmarkDotNet\Disassemblers\net461\win7-x86\BenchmarkDotNet.Disassembler.x86.exe
  BenchmarkDotNet.Annotations -> D:\projects\BenchmarkDotNet\src\BenchmarkDotNet.Annotations\bin\Release\netstandard2.0\BenchmarkDotNet.Annotations.dll
  BenchmarkDotNet -> D:\projects\BenchmarkDotNet\src\BenchmarkDotNet\bin\Release\netstandard2.0\BenchmarkDotNet.dll
  BenchmarkDotNet.Diagnostics.Windows -> D:\projects\BenchmarkDotNet\src\BenchmarkDotNet.Diagnostics.Windows\bin\Release\netstandard2.0\BenchmarkDotNet.Diagnostics.Windows.dll
  BenchmarkDotNet.Samples -> D:\projects\BenchmarkDotNet\samples\BenchmarkDotNet.Samples\bin\Release\net5.0\BenchmarkDotNet.Samples.dll
  BenchmarkDotNet.Autogenerated -> D:\projects\BenchmarkDotNet\samples\BenchmarkDotNet.Samples\bin\Release\net5.0\DefaultJob\bin\Release\net5.0\DefaultJob.dll
Build succeeded.
    0 Warning(s)
    0 Error(s)
Time Elapsed 00:00:02.17
// command took 2.39s and exited with 0
// ***** Done, took 00:00:03 (3.54 sec)   *****
// Found 2 benchmarks:
//   IntroBasic.Sleep: DefaultJob
//   IntroBasic.Thread.Sleep(10): DefaultJob

// The produced executable can be found at 'D:\projects\BenchmarkDotNet\samples\BenchmarkDotNet.Samples\bin\Release\net5.0\DefaultJob\bin\Release\net5.0\DefaultJob.dll'.

cc @Maoni0 @radical @AndyAyersMS

[Maoni0]

what's the usage scenario for this? how do you reuse this code? I guess this is not meant to keep the dll that contains the benchmarks so it doesn't get deleted by default? ie, an alternative way of doing `--keepFiles true"?

[adamsitnik]

what's the usage scenario for this? how do you reuse this code? I guess this is not meant to keep the dll that contains the benchmarks so it doesn't get deleted by default? ie, an alternative way of doing `--keepFiles true"?

The idea is that when you want to reuse the code produced by BDN to either debug or profile it, you just pass --justBuild and BDN builds the code, but does not run it. It just reports the path to the produced .dll/.exe, does not remove it and quits.

@Maoni0 is that going to be helpful?

[Maoni0]

@Maoni0 is that going to be helpful?

I have no idea :) I use BDN so little that I'm not sure what I can do with the dll that gets built. without an end to end scenario it's hard to me to tell what's useful and what's not.