Improvements to Roslyn command-line build experience

[KirillOsenkov]

• If one forgot to run Restore.cmd before build, detect that and print an error message: "You need to restore before building"
• If running Build.cmd from Developer Command Prompt, print a yellow warning: "WARNING: you are building from a Developer Command Prompt. We are bypassing isolated reproducible build and using the MSBuild and SDK from your command prompt instead. This may fail and is unsupported. Use a regular command prompt for a reliable reproducible build."
• Build.cmd should support a command-line argument to force reproducible build even if in Dev command prompt: -ignoreDevCommandPrompt

[jasonmalinowski]

@KirillOsenkov Should we break these out into separate issues? One issue means I can't assign to different people or say a commit fixes one issue in particular.

[KirillOsenkov]

I think it's up to @jaredpar - he asked me to file these.

[tannergooding]

One issue means I can't assign to different people

Can't you multi-assign an issue or PR?

[jaredpar]

Working on this today. Here is the conclusions I've come to about the builds

If one forgot to run Restore.cmd before build, detect that and print an error message: "You need to restore before building"

This is not possible to do correctly. Or rather doing a restore up to date check is as expensive as doing restore.

If running Build.cmd from Developer Command Prompt, print a yellow warning: "WARNING: you are building from a Developer Command Prompt. We are bypassing isolated reproducible build and using the MSBuild and SDK from your command prompt instead. This may fail and is unsupported. Use a regular command prompt for a reliable reproducible build."

Thought about this a lot over the last two days and decided on the following approach.

• If the Developer Command Prompt points to a compatible MSBuild instance then use that.
• else exit build.ps1 with at error saying the command prompt is incompatible.

I decided against using our xcopy MSBuild in this scenario. Due to the massive amount of environment changes in the Developer Command prompt it's hard to guarantee that this will work correctly.

Build.cmd should support a command-line argument to force reproducible build even if in Dev command prompt: -ignoreDevCommandPrompt

In order to implement this I would need to know the full set of environment variables set by the developer command prompt so that they could be unset. That is an ever changing list though hence not really possible. The version I could see doing here is knowing the set of allowed envirnoment variables and resetting the environment to that before building. In that case though we'd need to call it something like -cleanEnvironment.

[KirillOsenkov]

Understood.

If the Developer Command Prompt points to a compatible MSBuild instance then use that.
else exit build.ps1 with at error saying the command prompt is incompatible.

This is good enough.

[jaredpar]

#24544