Don't fail if there's nothing to do

I don't want the unit to fail if there is nothing to build, esp. since
it reports failures via email, and i have no need to distinguish between
different exit conditions right now.

build.sh

@@ -8,7 +8,7 @@ RELEASES="$(curl -s https://api.github.com/repos/M66B/FairEmail/releases)"
 LATEST_GITHUB_RELEASE=$(echo $RELEASES | jq '[.[] | select(.assets | length > 0)] | first')
 if [ "$LATEST_GITHUB_RELEASE" == null ]; then
     echo "No github release available"
-    exit 1
+    exit 0
 fi
 
 VERSION=$(echo $LATEST_GITHUB_RELEASE | jq -r '.tag_name')
@@ -16,7 +16,7 @@ APK_FILENAME=$(echo $LATEST_GITHUB_RELEASE | jq -r '.assets[0].name')
 
 if rsync sillywalk.de:/srv/www/sillywalk.de/root/releases/$APK_FILENAME; then
     echo "$APK_FILENAME already released. Aborting."
-    exit 1
+    exit 0
 fi
 
 KEYSTORE_FILE=$(cat $ANDROID_KEYSTORE_FILE | base64 -w0)
@@ -37,7 +37,7 @@ UPLOADED=$(rsync -i --ignore-existing apk/$APK_FILENAME sillywalk.de:/srv/www/si
 
 if [ -z "$UPLOADED" ]; then
     echo "$VERSION already uploaded. Aborting."
-    exit 1
+    exit 0
 fi
 
 export VERSION