tweak arg eval

Author: KodrAus

build/Build.Linux.ps1

@@ -78,7 +78,7 @@ foreach ($arch in $archs) {
     Build-DockerImage($arch)
 }
 
-if ($env:DOCKER_TOKEN -ne $null) {
+if ("$($env:DOCKER_TOKEN)" -ne "") {
     Login-ToDocker
 
     foreach ($arch in $archs) {

build/Build.Windows.ps1

@@ -126,7 +126,7 @@ Publish-DotNetTool($version)
 Execute-Tests($version)
 Publish-Docs($version)
 
-if ($env:NUGET_API_KEY -ne $null)
+if ("$($env:NUGET_API_KEY)" -ne "")
 {
     Upload-NugetPackages
 }