tweak appveyor script

appveyor.yml

@@ -11,6 +11,11 @@ branches:
     - /release-.*/
 install:
   - ps: "[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12"
+# if there's a newer build queued for the same PR, cancel this one
+  - ps: if ($env:APPVEYOR_PULL_REQUEST_NUMBER -and $env:APPVEYOR_BUILD_NUMBER -ne ((Invoke-RestMethod `
+        https://ci.appveyor.com/api/projects/$env:APPVEYOR_ACCOUNT_NAME/$env:APPVEYOR_PROJECT_SLUG/history?recordsNumber=50).builds | `
+        Where-Object pullRequestId -eq $env:APPVEYOR_PULL_REQUEST_NUMBER)[0].buildNumber) { `
+        throw "There are newer queued builds for this pull request, failing early." }
 # Download most recent Julia Windows binary
   - ps: (new-object net.webclient).DownloadFile(
         $env:JULIA_URL,
@@ -21,7 +26,8 @@ install:
 build_script:
 # Need to convert from shallow to complete for Pkg.clone to work
 #  - git fetch --unshallow
-  - C:\projects\julia\bin\julia -e "using InteractiveUtils; versioninfo(); import Pkg; Pkg.develop(pwd())"
+  - C:\projects\julia\bin\julia -e "using InteractiveUtils; versioninfo(); import Pkg;
+      Pkg.clone(pwd(), \"FileIO\"); Pkg.build(\"FileIO\")"
 
 test_script:
   - C:\projects\julia\bin\julia -e "import Pkg; Pkg.test(\"FileIO\")"