[Windows] move llvm to toolset (#4487)

images/win/scripts/Installers/Install-LLVM.ps1

@@ -0,0 +1,10 @@
+################################################################################
+##  File:  Install-LLVM.ps1
+##  Desc:  Install the latest stable version of llvm and clang compilers
+################################################################################
+
+$llvmVersion = (Get-ToolsetContent).llvm.version
+$latestChocoVersion = Get-LatestChocoPackageVersion -TargetVersion $llvmVersion -PackageName "llvm"
+Choco-Install -PackageName llvm -ArgumentList "--version $latestChocoVersion"
+
+Invoke-PesterTests -TestFile "LLVM"

images/win/scripts/Tests/LLVM.Tests.ps1

@@ -0,0 +1,7 @@
+Describe "Clang/LLVM" {
+    It "Clang/LLVM installed and version is correct" {
+        $toolsetVersion = (Get-ToolsetContent).llvm.version
+        $clangVersion = clang --version
+        $clangVersion[0] | Should -BeLike "*${toolsetVersion}*"
+    }
+}

images/win/scripts/Tests/Tools.Tests.ps1

@@ -81,15 +81,6 @@ Describe "KubernetesTools" {
     }
 }
 
-Describe "LLVM" {
-    It "<ToolName>" -TestCases @(
-        @{ ToolName = "clang" }
-        @{ ToolName = "clang++" }
-    ) {
-        "$ToolName --version" | Should -ReturnZeroExitCode
-    }
-}
-
 Describe "Mingw64" {
     It "<ToolName>" -TestCases @(
         @{ ToolName = "gcc" }