oandbackup: fix 0.3.0 (21)

Provide only arm support for now, see fdroid/fdroiddata#1366.

metadata/dk.jens.backup.txt

@@ -102,7 +102,18 @@ Build:0.2.13,20
 Build:0.3.0,21
     commit=0.3.0
     gradle=yes
-    rm=libs/*.jar
+    srclibs=rustup@1.14.0
+    build=$$rustup$$/rustup-init.sh -y && \
+        source $HOME/.cargo/env && \
+        rustup target add armv7-linux-androideabi && \
+        $$NDK$$/build/tools/make_standalone_toolchain.py --api 18 --install-dir=armv7_toolchain --arch=arm && \
+        cd oab-utils && \
+        mkdir .cargo && \
+        printf "[target.armv7-linux-androideabi]\n linker = \""$(realpath ../armv7_toolchain)"/bin/arm-linux-androideabi-clang\"" > .cargo/config && \
+        cargo build --release --target armv7-linux-androideabi && \
+        mkdir -p ../src/main/assets && \
+        cp -v target/*/release/oab-utils ../src/main/assets
+    ndk=r17b
 
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srclibs/rustup.txt

@@ -0,0 +1,2 @@
+Repo Type:git
+Repo:https://github.com/rust-lang-nursery/rustup.rs