Add Ubuntu Build+Test to Appveyor CI (#940)

* test using pwsh

* fix yaml syntax

* install platyps on pwsh

* appveyor still uses pwsh 6.0.0

* fix 1 test for pwsh. 1 remaining

* make test pending that is failing on pwsh on Windows as well.

* re-fix test for pwsh

* really fix test and simplify

* tweak and optimize appveyor.yml

* extract appveyor steps into ps module to eliminate code duplication

* fix and simplify test script

* fix path problem and put appveyor finish into module as well

* pwsh sessions are not being persisted on appveyor. Fix module deployment as well

* remove wmf4 image temporarily to run it on the fork again

* revert test script to non-module version because some tests failed

* try fix yaml syntax

* use consistent space and try $ErrorActionPreference = 'Stop' in appveyor module

* fix appveyorfinish for pwsh and give test-appveyor function a last try

* take out invoke-appveyortest method since it does not work in the appveyor environment

* add wmf4 image as it is ready for PW now.

* install platyps in a wmf4 friendly way

* let's try if we can remove the hard coded checkout path (fingers crossed this works in WMF as well)

* let's try if we can rename the PowerShellEdition to something more meaningful (again fingers crossed for the WMF 4 build)

* Set DOTNET_SKIP_FIRST_TIME_EXPERIENCE to 1 to speed-up WMF4 builds, which have to install the .net sdk from scratch

* make indentation consistent after rename

* remove setting PATH for psmodulepath in yaml (not needed for VS 2017 image, let's hope it works for WMF 4 as well)

* try ubuntu image

* fix ps edition

* fix test for linux

* add debugging code

* fix case sensitivity problems

* re-add other images for PR

* git mv rules\UseSupportsShouldProcess.cs Rules\UseSupportsShouldProcess.cs

Author: bergmeister

rules/UseSupportsShouldProcess.cs Rules/UseSupportsShouldProcess.csrules/UseSupportsShouldProcess.cs renamed to Rules/UseSupportsShouldProcess.cs

@@ -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