Fix condition

Author: lrytz

scripts/common.ps1

@@ -1,5 +1,5 @@
 Function postCommitStatus($state) {
-  if ($env:scala_sha -ne '') {
+  if ("$env:scala_sha" -ne "") {
     $jsonTemplate = '{{ "state": "{0}", "target_url": "{1}", "description": "{2}", "context": "{3}" }}'
     $json = "$jsonTemplate" -f "$state", "https://ci.appveyor.com/project/scala/scala-dist/build/$env:APPVEYOR_BUILD_ID", "$state", "appveyor/scala-dist/$env:version/$env:mode"