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When proguard is enabled building the Android client fails because the command line used to execute proguard is too long for Windows systems.

Shortened output:
[INFO] C:\Program Files\Java\jdk1.7.0_02\jre\bin\java [-Xmx512M, -jar, C:\Program Files (x86)\Android\android-sdk\tools\proguard\lib\proguard.jar, @proguard.cfg, -injars, 'C:\Users\Dirk\git\ecard-client\clients\android\target\classes', -injars, C:\Users\Dirk\.m2\repository\org\openecard\common\1.1.0-SNAPSHOT\common-1.1.0-SNAPSHOT.jar(!META-INF/maven/**,!META-INF/MANIFEST.MF), .......
[INFO] Die Befehlszeile ist zu lang.

Maximum length for command lines on Windows systems (XP and higher) is 8191 characters but the generated command line is about 500 characters longer.

Issue #218 implements a workaround. However a different android plugin should be used or a patch for the plugin should be provided, so that proguard can run under windows as well.