fix: Resolve EACCESS error in special cases (#2135)

Co-authored-by: oSumAtrIX <johan.melkonyan1@web.de>

android/app/src/main/kotlin/app/revanced/manager/flutter/MainActivity.kt

@@ -219,6 +219,9 @@ class MainActivity : FlutterActivity() {
         keystorePassword: String
     ) {
         val inFile = File(inFilePath)
+        // Necessary because the file is copied from a nonwriteable location.
+        inFile.setWritable(true)
+        inFile.setReadable(true)
         val outFile = File(outFilePath)
         val integrations = File(integrationsPath)
         val keyStoreFile = File(keyStoreFilePath)