ci: android: Use signing key if available

Lets gradle handle apk signing when available

.ci/scripts/android/build.sh

@@ -8,8 +8,17 @@ ccache -s
 
 BUILD_FLAVOR=mainline
 
+if [ ! -z "${ANDROID_KEYSTORE_B64}" ]; then
+    export ANDROID_KEYSTORE_FILE="${GITHUB_WORKSPACE}/ks.jks"
+    base64 --decode <<< "${ANDROID_KEYSTORE_B64}" > "${ANDROID_KEYSTORE_FILE}"
+fi
+
 cd src/android
 chmod +x ./gradlew
 ./gradlew "assemble${BUILD_FLAVOR}Release" "bundle${BUILD_FLAVOR}Release"
 
 ccache -s
+
+if [ ! -z "${ANDROID_KEYSTORE_B64}" ]; then
+    rm "${ANDROID_KEYSTORE_FILE}"
+fi

.ci/scripts/android/upload.sh

@@ -13,15 +13,3 @@ cp src/android/app/build/outputs/apk/"${BUILD_FLAVOR}/release/app-${BUILD_FLAVOR
   "artifacts/${REV_NAME}.apk"
 cp src/android/app/build/outputs/bundle/"${BUILD_FLAVOR}Release"/"app-${BUILD_FLAVOR}-release.aab" \
   "artifacts/${REV_NAME}.aab"
-
-if [ -n "${ANDROID_KEYSTORE_B64}" ]
-then
-  echo "Signing apk..."
-  base64 --decode <<< "${ANDROID_KEYSTORE_B64}" > ks.jks
-
-  apksigner sign --ks ks.jks \
-    --ks-key-alias "${ANDROID_KEY_ALIAS}" \
-    --ks-pass env:ANDROID_KEYSTORE_PASS "artifacts/${REV_NAME}.apk"
-else
-  echo "No keystore specified, not signing the APK files."
-fi