build\build.ps1 fails on clean environment

[anpaz]

Describe the bug

I'm trying to run build.ps1 and found a couple of blockers:

1. It requires to have Chocolatey installed.

• Even worse, it then requires to run the build script as an admin to install llvm

2. It failed to compile src\QsFmt\Parser\Parser.csproj, apparently this requires java

To Reproduce

Steps to reproduce the behavior:

1. Clone the repo from https://github.com/microsoft/qsharp-compiler.git
2. Run .\bootstrap.ps1
3. Run .\build\build.ps1

Expected behavior

This pre-reqs should be listed in the README.md, or at least in the build folder. Ideally, this would be optional and if not installed the corresponding components should be skipped. For Chocolatey, it should install these dependencies in some location that doesn't require the build to run on an elevated prompt.

System information

> dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.204
 Commit:    84d1fe1bb7

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.204\

Host (useful for support):
  Version: 5.0.7
  Commit:  556582d964