Change sign-apk to work with JDK 7

The -sigalg and -digestalg arguments for jarsigner need to be explicitly
set to MD5withRSA and SHA1 respectively in order for signing to work
when using JDK 7.

See
http://developer.android.com/tools/publishing/app-signing.html#signapp

src/leiningen/droid/build.clj

@@ -163,6 +163,8 @@
       (create-debug-keystore keystore-path))
     (ensure-paths unaligned-path keystore-path)
     (sh "jarsigner"
+        "-sigalg" "MD5withRSA"
+        "-digestalg" "SHA1"
         "-keystore" keystore-path
         "-storepass" storepass
         "-keypass" keypass