Support shared .NET installation

[NikolaMilosavljevic]

Fixes: dotnet/source-build#5408

VMR's Tag & Scan stage runs multiple commands that require .NET. All scripts in the stage assumed that .NET is installed locally, to .dotnet. Installation is done via arcade's InitializeDotNetCli function (in eng/common/tools.sh).

InitializeDotNetCli skips .NET installation if the machine has the required version installed to a shared location. InitializeDotNetCli sets the _InitializeDotNetCli to the .NET path, local or shared.

The fix is to use the .NET path that was obtained with InitializeDotNetCli.

Validation build

[MichaelSimons]

I'm not a fan of being broken by changes to in the build agent. Thoughts on containerizing this stage to better isolate ourselves against these types of breaks?

[NikolaMilosavljevic]

I'm not a fan of being broken by changes to in the build agent. Thoughts on containerizing this stage to better isolate ourselves against these types of breaks?

We could do that, but my fix is simply allowing us to use whichever .NET installation was provided by InitializeDotNetCli. We don't need to know where it's installed or whether it was preinstalled on the machine beforehand.

Created an issue for improvements in resiliency of Tag & Scan stage - dotnet/source-build#5418

[MichaelSimons]

I'm not a fan of being broken by changes to in the build agent. Thoughts on containerizing this stage to better isolate ourselves against these types of breaks?

We could do that, but my fix is simply allowing us to use whichever .NET installation was provided by InitializeDotNetCli. We don't need to know where it's installed or whether it was preinstalled on the machine beforehand.

Created an issue for improvements in resiliency of Tag & Scan stage - dotnet/source-build#5418

Per offline discussion, both our comments are complimentary to each other. dotnet/source-build#5418 was logged to ensure a resilient solution is in place in main going forward that we can decide on backporting.

[NikolaMilosavljevic]

Failing check is unrelated to my changes. This is an infra change - merging.