validate the expected output package exists (#4795)

build.psm1

@@ -702,7 +702,7 @@ function New-PSOptions {
 
     if($RootInfo.RepoPath -ne $RootInfo.ValidPath)
     {
-        $RootInfo['Warning'] = "Please ensure you repo is at the root of the file system and named 'PowerShell' (example: '$($RootInfo.ValidPath)'), when building and packaging for release!"
+        $RootInfo['Warning'] = "Please ensure your repo is at the root of the file system and named 'PowerShell' (example: '$($RootInfo.ValidPath)'), when building and packaging for release!"
         $RootInfo['IsValid'] = $false
     }
     else
@@ -1837,8 +1837,15 @@ function New-MSIPackage
 
     Remove-Item -ErrorAction SilentlyContinue *.wixpdb -Force
 
-    Write-Verbose "You can find the MSI @ $msiLocationPath" -Verbose
-    $msiLocationPath
+    if (Test-Path $msiLocationPath)
+    {
+        Write-Verbose "You can find the MSI @ $msiLocationPath" -Verbose
+        $msiLocationPath
+    }
+    else
+    {
+        throw "Failed to create $msiLocationPath"
+    }
 }
 
 function Start-CrossGen {

tools/packaging/packaging.psm1

@@ -540,7 +540,14 @@ function New-UnixPackage {
         }
     }
 
-    return $createdPackage
+    if (Test-Path $createdPackage)
+    {
+        return $createdPackage
+    }
+    else
+    {
+        throw "Failed to create $createdPackage"
+    }
 }
 
 function New-StagingFolder
@@ -628,9 +635,15 @@ function New-ZipPackage
             Compress-Archive -Path $PackageSourcePath\* -DestinationPath $zipLocationPath
         }
 
-        log "You can find the Zip @ $zipLocationPath"
-        $zipLocationPath
-
+        if (Test-Path $zipLocationPath)
+        {
+            log "You can find the Zip @ $zipLocationPath"
+            $zipLocationPath
+        }
+        else
+        {
+            throw "Failed to create $zipLocationPath"
+        }
     }
     #TODO: Use .NET Api to do compresss-archive equivalent if the pscmdlet is not present
     else
@@ -712,7 +725,15 @@ function New-NugetPackage
     log "Use -verbose to see output..."
     Start-NativeExecution -sb {dotnet $arguments} | Foreach-Object {Write-Verbose $_}
 
-    Get-ChildItem $nugetFolder\* | Select-Object -ExpandProperty FullName
+    $nupkgFile = "${nugetFolder}\${nuspecPackageName}-${packageRuntime}.${nugetSemanticVersion}.nupkg"
+    if (Test-Path $nupkgFile)
+    {
+        Get-ChildItem $nugetFolder\* | Select-Object -ExpandProperty FullName
+    }
+    else
+    {
+        throw "Failed to create $nupkgFile"
+    }
 }
 
 function New-SubFolder