Fix native library version in FBReader 2.5.9

Was being built with a native library only compatible with android-21
and above.  Since the min supported version should be android-11, added
a command to prebuild to force android-11 in the jni.

metadata/org.geometerplus.zlibrary.ui.android.txt

@@ -337,6 +337,7 @@ Build:2.5.9-ics,2050920
         cp local.properties third-party/AmbilWarna/ && \
         cp local.properties third-party/android-filechooser/code/ && \
         cp local.properties third-party/drag-sort-listview/library/ && \
+        echo 'APP_PLATFORM := android-11' >> jni/Application.mk && \
         pushd $$ApacheHttpClient$$/httpmime/ && \
         $$MVN3$$ package -Dmaven.javadoc.skip=true && \
         popd && \