Bring Host build into separate project

build_projects/dotnet-host-build/build.ps1

@@ -0,0 +1,81 @@
+#
+# Copyright (c) .NET Foundation and contributors. All rights reserved.
+# Licensed under the MIT license. See LICENSE file in the project root for full license information.
+#
+
+param(
+    [string]$Configuration="Debug",
+    [string]$Architecture="x64",
+    [string[]]$Targets=@("Default"),
+    [switch]$NoPackage,
+    [switch]$Help)
+
+if($Help)
+{
+    Write-Host "Usage: .\build.ps1 [-Configuration <CONFIGURATION>] [-NoPackage] [-Help] [-Targets <TARGETS...>]"
+    Write-Host ""
+    Write-Host "Options:"
+    Write-Host "  -Configuration <CONFIGURATION>     Build the specified Configuration (Debug or Release, default: Debug)"
+    Write-Host "  -Architecture  <ARCHITECTURE>      Build the specified architecture (x64 or x86 (supported only on Windows), default: x64)"
+    Write-Host "  -Targets <TARGETS...>              Comma separated build targets to run (Init, Compile, Publish, etc.; Default is a full build and publish)"
+    Write-Host "  -NoPackage                         Skip packaging targets"
+    Write-Host "  -Help                              Display this help message"
+    exit 0
+}
+
+$env:CONFIGURATION = $Configuration;
+$RepoRoot = "$PSScriptRoot\..\.."
+
+if($NoPackage)
+{
+    $env:DOTNET_BUILD_SKIP_PACKAGING=1
+}
+else
+{
+    $env:DOTNET_BUILD_SKIP_PACKAGING=0
+}
+
+# Load Branch Info
+cat "$RepoRoot\branchinfo.txt" | ForEach-Object {
+    if(!$_.StartsWith("#") -and ![String]::IsNullOrWhiteSpace($_)) {
+        $splat = $_.Split([char[]]@("="), 2)
+        Set-Content "env:\$($splat[0])" -Value $splat[1]
+    }
+}
+
+# Use a repo-local install directory (but not the artifacts directory because that gets cleaned a lot
+if (!$env:DOTNET_INSTALL_DIR)
+{
+    $env:DOTNET_INSTALL_DIR="$RepoRoot\.dotnet_stage0\Windows\$Architecture"
+}
+
+if (!(Test-Path $env:DOTNET_INSTALL_DIR))
+{
+    mkdir $env:DOTNET_INSTALL_DIR | Out-Null
+}
+
+# Install a stage 0
+Write-Host "Installing .NET Core CLI Stage 0 from branchinfo channel"
+& "$RepoRoot\scripts\obtain\dotnet-install.ps1" -Channel $env:CHANNEL -Architecture $Architecture -Verbose
+if($LASTEXITCODE -ne 0) { throw "Failed to install stage0" }
+
+# Put the stage0 on the path
+$env:PATH = "$env:DOTNET_INSTALL_DIR;$env:PATH"
+
+# Restore the build scripts
+Write-Host "Restoring Build Script projects..."
+pushd "$PSScriptRoot\.."
+dotnet restore --infer-runtimes
+if($LASTEXITCODE -ne 0) { throw "Failed to restore" }
+popd
+
+# Publish the builder
+Write-Host "Compiling Build Scripts..."
+dotnet publish "$PSScriptRoot" -o "$PSScriptRoot\bin" --framework netcoreapp1.0
+if($LASTEXITCODE -ne 0) { throw "Failed to compile build scripts" }
+
+# Run the builder
+Write-Host "Invoking Build Scripts..."
+Write-Host " Configuration: $env:CONFIGURATION"
+& "$PSScriptRoot\bin\dotnet-host-build.exe" @Targets
+if($LASTEXITCODE -ne 0) { throw "Build failed" }