app-unpriv: Set ndkVersion as well for stripping

Otherwise, the stripping step always fails in CI builds. This breaks
reproducibility as debug info contains path to NDK.

app-unpriv/build.gradle.kts

@@ -18,6 +18,7 @@ apply {
 android {
     namespace = "im.angry.easyeuicc"
     compileSdk = 34
+    ndkVersion = "26.1.10909125"
 
     defaultConfig {
         applicationId = "im.angry.easyeuicc"