GreenBits: ANDROID_NDK value debugging, updated to 1.33

- explicit ANDROID_NDK value
 - echo statements to see if the value changes
 - re-enabled the build

metadata/com.greenaddress.greenbits_android_wallet.txt

@@ -26,20 +26,22 @@ You can find it at [[it.greenaddress.cordova]].
 Repo Type:git
 Repo:https://github.com/greenaddress/GreenBits
 
-Build:1.32,32
-    disable=wip
-    commit=1.32
+Build:1.33,33
+    commit=1.33
     subdir=app
     submodules=yes
     gradle=production
     srclibs=AutobahnSW-greenaddress@fb1223083dc6e9dfddc0daad3b76dae277765b51
     rm=app/libs/*.jar
-    prebuild=pushd $$AutobahnSW-greenaddress$$ && \
+    prebuild=echo "ANDROID_NDK in prebuild (not setting it): $ANDROID_NDK" && \
+        pushd $$AutobahnSW-greenaddress$$ && \
         $$MVN3$$ package && \
         popd && \
         cp $$AutobahnSW-greenaddress$$/target/autobahn-android-sw-0.5.2-SNAPSHOT.jar libs/
     scandelete=app/src/main/jniLibs/armeabi/libscrypt.so,app/src/main/jniLibs/mips/libscrypt.so,app/src/main/jniLibs/x86/libscrypt.so,app/scrypt/src
-    build=./prepare_fdroid.sh
+    build=echo "ANDROID_NDK in build before setting: $ANDROID_NDK" && \
+        ANDROID_NDK=$$NDK$$ sh -c 'echo "ANDROID_NDK in build after setting: $ANDROID_NDK"' && \
+        ANDROID_NDK=$$NDK$$ ./prepare_fdroid.sh
 
 Maintainer Notes:
 scandelete libscrypt.so - it is built by F-Droid via prepare_fdroid.sh,