Fixed build for Barcode scanner 4.6.3 (98)

Probably a better solution would be to fix upstream's root pom.xml,
since it pulls lot of un-necessary packages (some even cannot be
found!), and use maven instead of ant to build

metadata/com.google.zxing.client.android.txt

@@ -76,7 +76,9 @@ Build:4.6.2,97
 
 Build:4.6.3,98
     commit=BS-4.6.3
+    target=android-19
     subdir=android
+    prebuild=echo "java.source=7\njava.target=7" >> local.properties
     build=$$MVN3$$ package -f ../core/pom.xml
 
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