Merge the microbuild branch from https://github.com/aarnott/Library.Template

Specifically, this merges [5c12a14 from that repo](AArnott/Library.Template@5c12a14).

Author: AArnott

tools/Convert-PDB.ps1

@@ -35,7 +35,10 @@ catch {
     return
 }
 
-New-Item -ItemType Directory -Force -Path (Split-Path $OutputPath -Parent) | Out-Null
+$outputDirectory = Split-Path $OutputPath -Parent
+if ($outputDirectory) {
+    New-Item -ItemType Directory -Force -Path $outputDirectory | Out-Null
+}
 
 $toolpath = "$pdb2pdbpath/tools/Pdb2Pdb.exe"
 $arguments = $DllPath, '/out', $OutputPath, '/nowarn', '0021'

tools/Get-ExternalSymbolFiles.ps1

@@ -93,7 +93,7 @@ Function Get-PackageVersions() {
 }
 
 Function Get-PackageVersion($id) {
-    $version = Get-PackageVersions | Select-Object -ExpandProperty $id -ErrorAction SilentlyContinue
+    $version = (Get-PackageVersions)[$id]
     if (!$version) {
         Write-Error "No package version found in Directory.Packages.props for the package '$id'"
     }

tools/Install-NuGetPackage.ps1

@@ -57,7 +57,7 @@ $nugetArgs += '-Verbosity',$Verbosity
 if ($PSCmdlet.ShouldProcess($PackageId, 'nuget install')) {
     $p = Start-Process $nugetPath $nugetArgs -NoNewWindow -Wait -PassThru
     if ($null -ne $p.ExitCode -and $p.ExitCode -ne 0) {
-        throw "NuGet install failed for package '$PackageId' (version '$requestedVersion') with exit code $exitCode."
+        throw "NuGet install failed for package '$PackageId' (version '$Version') with exit code $($p.ExitCode)."
     }
 }