Add systemd service on ARM builds

Raspbian uses systemd. Unfortunately the ARM build for the deb package doesn't provide them. It's very useful though for auto start after network is on.

release/arch/arm/build-arm.sh

@@ -91,6 +91,11 @@ mkdir -p duniter-${ARCH}/opt/duniter/
 chmod 755 duniter-${ARCH}/DEBIAN/post*
 chmod 755 duniter-${ARCH}/DEBIAN/pre*
 sed -i "s/Version:.*/Version:$DUNITER_DEB_VER/g" duniter-${ARCH}/DEBIAN/control
+
+#Systemd service
+mkdir -p duniter-${ARCH}/lib/systemd/system
+mv duniter_release/release/extra/systemd/duniter.service duniter-${ARCH}/lib/systemd/system/
+
 cd duniter_release
 pwd
 rm -Rf .git