Added install_llvmpipe script to replace -nographics in Windows builds (#706)

* Added install_llvmpipe script

* Replace ternary with a regular condition

* Revert files I haven't changed

* Pin llvmpipe version, expand test matrix with a single enableGPU target

* Fixed parameter name

* EnableGPU false by default

* Fixed nitpick

* Fixed scripts

* Pass enableGpu into tests properly

* Fixed script

* Append With GPU to build name

* Fix expression

dist/platforms/windows/entrypoint.ps1

@@ -13,6 +13,11 @@ Get-Process -Name regsvr32 | ForEach-Object { Stop-Process -Id $_.Id -Force }
 # Setup Git Credentials
 . "c:\steps\set_gitcredential.ps1"
 
+if ($env:ENABLE_GPU -eq "true") {
+  # Install LLVMpipe software graphics driver
+  . "c:\steps\install_llvmpipe.ps1"
+}
+
 # Activate Unity
 if ($env:SKIP_ACTIVATION -ne "true") {
   . "c:\steps\activate.ps1"