Let's try this

build.ps1

@@ -362,6 +362,11 @@ try {
 
     $toolsetBuildProj = InitializeToolset
 
+    $sdkPath = [IO.Path]::Combine($env:DOTNET_INSTALL_DIR, 'sdk', '3.1.102')
+    if (!(Test-Path $sdkPath)) {
+        InstallDotNetSdk $dotnetRoot '3.1.102-servicing-014873' -skipNonVersionedFiles $true
+    }
+
     $restore = $tmpRestore
 
     if ($ci) {

build.sh

@@ -316,6 +316,8 @@ restore=true
 
 InitializeToolset
 
+InstallDotNetSdk "$DOTNET_INSTALL_DIR" "3.1.102-servicing-014873"
+
 restore=$_tmp_restore=
 
 if [ "$build_repo_tasks" = true ]; then

eng/common/tools.ps1

@@ -139,6 +139,7 @@ function InitializeDotNetCli([bool]$install) {
         InstallDotNetSdk $dotnetRoot $dotnetSdkVersion
       } else {
         Write-PipelineTelemetryError -Category "InitializeToolset" -Message "Unable to find dotnet with SDK version '$dotnetSdkVersion'"
+        ExitWithExitCode 1
       }
     }
 
@@ -183,7 +184,7 @@ function InstallDotNetSdk([string] $dotnetRoot, [string] $version, [string] $arc
   InstallDotNet $dotnetRoot $version $architecture
 }
 
-function InstallDotNet([string] $dotnetRoot, [string] $version, [string] $architecture = "", [string] $runtime = "", [bool] $skipNonVersionedFiles = $true) {
+function InstallDotNet([string] $dotnetRoot, [string] $version, [string] $architecture = "", [string] $runtime = "", [bool] $skipNonVersionedFiles = $false) {
   $installScript = GetDotNetInstallScript $dotnetRoot
   $installParameters = @{
     Version = $version

eng/common/tools.sh

@@ -41,7 +41,7 @@ fi
 # Configures warning treatment in msbuild.
 warn_as_error=${warn_as_error:-true}
 
-# True to attempt using .NET Core already that meets requirements specified in global.json
+# True to attempt using .NET Core already that meets requirements specified in global.json 
 # installed on the machine instead of downloading one.
 use_installed_dotnet_cli=${use_installed_dotnet_cli:-true}
 
@@ -143,6 +143,7 @@ function InitializeDotNetCli {
         InstallDotNetSdk "$dotnet_root" "$dotnet_sdk_version"
       else
         Write-PipelineTelemetryError -category 'InitializeToolset' "Unable to find dotnet with SDK version '$dotnet_sdk_version'"
+        ExitWithExitCode 1
       fi
     fi
   fi
@@ -180,7 +181,7 @@ function InstallDotNetSdk {
 function InstallDotNet {
   local root=$1
   local version=$2
-
+ 
   GetDotNetInstallScript "$root"
   local install_script=$_GetDotNetInstallScript
 
@@ -221,7 +222,7 @@ function GetDotNetInstallScript {
         Write-PipelineTelemetryError -category 'InitializeToolset' "Failed to acquire dotnet install script (exit code '$exit_code')."
         ExitWithExitCode $exit_code
       }
-    else
+    else 
       wget -q -O "$install_script" "$install_script_url" || {
         local exit_code=$?
         Write-PipelineTelemetryError -category 'InitializeToolset' "Failed to acquire dotnet install script (exit code '$exit_code')."
@@ -237,11 +238,11 @@ function InitializeBuildTool {
   if [[ -n "${_InitializeBuildTool:-}" ]]; then
     return
   fi
-
+  
   InitializeDotNetCli $restore
 
   # return values
-  _InitializeBuildTool="$_InitializeDotNetCli/dotnet"
+  _InitializeBuildTool="$_InitializeDotNetCli/dotnet"  
   _InitializeBuildToolCommand="msbuild"
   _InitializeBuildToolFramework="netcoreapp2.1"
 }
@@ -302,7 +303,7 @@ function InitializeToolset {
   if [[ "$binary_log" == true ]]; then
     bl="/bl:$log_dir/ToolsetRestore.binlog"
   fi
-
+  
   echo '<Project Sdk="Microsoft.DotNet.Arcade.Sdk"/>' > "$proj"
   MSBuild-Core "$proj" $bl /t:__WriteToolsetLocation /clp:ErrorsOnly\;NoSummary /p:__ToolsetLocationOutputFile="$toolset_location_file"
 

global.json

@@ -1,9 +1,9 @@
 {
   "sdk": {
-    "version": "3.1.102-servicing-014873"
+    "version": "3.1.101"
   },
   "tools": {
-    "dotnet": "3.1.102-servicing-014873",
+    "dotnet": "3.1.101",
     "runtimes": {
       "dotnet/x64": [
         "$(MicrosoftNETCoreAppInternalPackageVersion)"