Update dependencies from https://github.com/dotnet/arcade build 20191216.4 (#5904)

- Microsoft.DotNet.Arcade.Sdk - 5.0.0-beta.19616.4

eng/common/tools.ps1

@@ -98,6 +98,9 @@ function Exec-Process([string]$command, [string]$commandArgs) {
   }
 }
 
+# createSdkLocationFile parameter enables a file being generated under the toolset directory
+# which writes the sdk's location into. This is only necessary for cmd --> powershell invocations
+# as dot sourcing isn't possible.
 function InitializeDotNetCli([bool]$install, [bool]$createSdkLocationFile) {
   if (Test-Path variable:global:_DotNetInstallDir) {
     return $global:_DotNetInstallDir
@@ -146,21 +149,23 @@ function InitializeDotNetCli([bool]$install, [bool]$createSdkLocationFile) {
     }
 
     $env:DOTNET_INSTALL_DIR = $dotnetRoot
+  }
 
-    if ($createSdkLocationFile) {
-      # Create a temporary file under the toolset dir and rename it to sdk.txt to avoid races.
-      do { 
-        $sdkCacheFileTemp = Join-Path $ToolsetDir $([System.IO.Path]::GetRandomFileName())
-      } 
-      until (!(Test-Path $sdkCacheFileTemp))
-      Set-Content -Path $sdkCacheFileTemp -Value $dotnetRoot
-
-      try {
-        Rename-Item -Force -Path $sdkCacheFileTemp 'sdk.txt'
-      } catch {
-        # Somebody beat us
-        Remove-Item -Path $sdkCacheFileTemp
-      }
+  # Creates a temporary file under the toolset dir.
+  # The following code block is protecting against concurrent access so that this function can
+  # be called in parallel.
+  if ($createSdkLocationFile) {
+    do { 
+      $sdkCacheFileTemp = Join-Path $ToolsetDir $([System.IO.Path]::GetRandomFileName())
+    } 
+    until (!(Test-Path $sdkCacheFileTemp))
+    Set-Content -Path $sdkCacheFileTemp -Value $dotnetRoot
+  
+    try {
+      Rename-Item -Force -Path $sdkCacheFileTemp 'sdk.txt'
+    } catch {
+      # Somebody beat us
+      Remove-Item -Path $sdkCacheFileTemp
     }
   }