Add Ubuntu Build+Test to Appveyor CI

appveyor.yml

@@ -9,15 +9,17 @@ environment:
   - APPVEYOR_BUILD_WORKER_IMAGE: WMF 4
     PowerShellEdition: WindowsPowerShell
     BuildConfiguration: PSv3Release
+  - APPVEYOR_BUILD_WORKER_IMAGE: Ubuntu
+    PowerShellEdition: PowerShellCore
+    BuildConfiguration: Release
 
 # cache Nuget packages and dotnet CLI cache
 cache:
   - '%USERPROFILE%\.nuget\packages -> appveyor.yml'
   - '%LocalAppData%\Microsoft\dotnet -> appveyor.yml'
 
 install:
-  - ps: Import-Module .\tools\appveyor.psm1
-  - ps:   if ($env:PowerShellEdition -eq 'WindowsPowerShell') { Invoke-AppveyorInstall }
+  - ps:   if ($env:PowerShellEdition -eq 'WindowsPowerShell') { Import-Module .\tools\appveyor.psm1; Invoke-AppveyorInstall }
   - pwsh: if ($env:PowerShellEdition -eq 'PowerShellCore')    { Import-Module .\tools\appveyor.psm1; Invoke-AppveyorInstall }
 
 build_script:
@@ -47,7 +49,7 @@ test_script:
             }
   - pwsh: |
             if ($env:PowerShellEdition -eq 'PowerShellCore') {
-                $modulePath = $env:PSModulePath.Split(';') | Where-Object { Test-Path $_} | Select-Object -First 1
+                $modulePath = $env:PSModulePath.Split([System.IO.Path]::PathSeparator) | Where-Object { Test-Path $_} | Select-Object -First 1
                 Copy-Item "${env:APPVEYOR_BUILD_FOLDER}\out\PSScriptAnalyzer" "$modulePath\" -Recurse -Force
                 $testResultsFile = ".\TestResults.xml"
                 $testScripts = "${env:APPVEYOR_BUILD_FOLDER}\Tests\Engine","${env:APPVEYOR_BUILD_FOLDER}\Tests\Rules"
@@ -60,4 +62,4 @@ test_script:
 
 # Upload the project along with test results as a zip archive
 on_finish:
-  - ps: Invoke-AppveyorFinish
+  - ps: Import-Module .\tools\appveyor.psm1; Invoke-AppveyorFinish