CI: download the proxy jar also on mingw

We were downloading the jar from within an block which only runs for
MSVC. Move the download to the start of the test so it gets downloaded
for both.

appveyor.yml

@@ -27,19 +27,20 @@ build_script:
     if ($env:GENERATOR -ne "MSYS Makefiles") {
       cmake -D ENABLE_TRACE=ON -D BUILD_CLAR=ON -D MSVC_CRTDBG=ON .. -G"$env:GENERATOR"
       cmake --build . --config Debug
-      Invoke-WebRequest https://github.com/ethomson/poxyproxy/releases/download/v0.1.0/poxyproxy-0.1.0.jar -OutFile poxyproxy.jar
     }
 - cmd: |
     if "%GENERATOR%"=="MSYS Makefiles" (C:\MinGW\msys\1.0\bin\sh --login /c/projects/libgit2/script/appveyor-mingw.sh)
 test_script:
 - ps: |
     $ErrorActionPreference="Stop"
+    Invoke-WebRequest https://github.com/ethomson/poxyproxy/releases/download/v0.1.0/poxyproxy-0.1.0.jar -OutFile poxyproxy.jar
     # Run this early so we know it's ready by the time we need it
-    Start-Job { java -jar $Env:APPVEYOR_BUILD_FOLDER\build\poxyproxy.jar -d --port 8080 --credentials foo:bar }
+    $proxyJob = Start-Job { java -jar $Env:APPVEYOR_BUILD_FOLDER\build\poxyproxy.jar -d --port 8080 --credentials foo:bar }
     ctest -V -R libgit2_clar
     $env:GITTEST_REMOTE_URL="https://github.com/libgit2/non-existent"
     $env:GITTEST_REMOTE_USER="libgit2test"
     ctest -V -R libgit2_clar-cred_callback
+    Receive-Job -Job $proxyJob
     $env:GITTEST_REMOTE_PROXY_URL = "http://foo:bar@localhost:8080"
     ctest -V -R libgit2_clar-proxy_credentials_in_url
     $env:GITTEST_REMOTE_PROXY_URL = "http://localhost:8080"