do not set host path

Author: dibarbet

eng/build.ps1

@@ -734,15 +734,6 @@ try {
 
   Push-Location $RepoRoot
 
-  # Workaround for DOTNET_HOST_PATH not being set by older MSBuild
-  # Removal is tracked by https://github.com/dotnet/roslyn/issues/80742
-  if (-not $env:DOTNET_HOST_PATH) {
-    $env:DOTNET_HOST_PATH = Join-Path (Join-Path $RepoRoot '.dotnet') 'dotnet'
-    if (-not (Test-Path $env:DOTNET_HOST_PATH)) {
-      $env:DOTNET_HOST_PATH = "$($env:DOTNET_HOST_PATH).exe"
-    }
-  }
-
   Subst-TempDir
 
   if ($ci) {
@@ -759,6 +750,18 @@ try {
     &(Ensure-DotNetSdk) tool restore
   }
 
+  # Above InitializeDotNetCli or Ensure-DotNetSdk may have installed a local .NET SDK (stored in global:_DotNetInstallDir).
+  # We need to make sure DOTNET_HOST_PATH points to that SDK as a workaround for older MSBuild
+  # which will not set it correctly.  Removal is tracked by https://github.com/dotnet/roslyn/issues/80742
+  if (-not $env:DOTNET_HOST_PATH -and (Test-Path variable:global:_DotNetInstallDir)) {
+    $env:DOTNET_HOST_PATH = Join-Path $global:_DotNetInstallDir 'dotnet'
+    if (-not (Test-Path $env:DOTNET_HOST_PATH)) {
+      $env:DOTNET_HOST_PATH = "$($env:DOTNET_HOST_PATH).exe"
+    }
+
+    Write-Host "Setting DOTNET_HOST_PATH to $env:DOTNET_HOST_PATH"
+  }
+
   if ($bootstrap -and $bootstrapDir -eq "") {
     Write-Host "Building bootstrap Compiler"
     $bootstrapDir = Join-Path (Join-Path $ArtifactsDir "bootstrap") "build"