Update appveyor.yml

hm, looks like leiningen isn't actually accessible from bash; let's try to fix that...

appveyor.yml

@@ -40,6 +40,8 @@ install:
   - ps: $SPIDERMONKEY_HOME = "$pwd/jsshell"
   - ps: $env:CHAKRACORE_HOME = "$pwd/chakra-core/x64_release"
   - ps: $CHAKRACORE_HOME = "$pwd/chakra-core/x64_release"
+  - cmd: appveyor-retry pacman -Syuu --needed --noconfirm --noprogressbar --ask=127
+  - cmd: appveyor-retry pacman -S --noconfirm clojure leiningen
 
 test_script:
   - cmd: bash -cvx "lein test || lein test-all || mvn test || mvn test-compile || mvn generate-test-sources || mvn process-test-sources || mvn generate-test-resources || mvn process-test-resources || mvn process-test-classes || mvn pre-integration-test || mvn integration-test || mvn post-integration-test || mvn verify || lein check || lein check-all || lein compile || lein javac || lein retest"