Fix direct install on NAND devices

Co-authored-by: John Wu <topjohnwu@gmail.com>

app/src/main/java/com/topjohnwu/magisk/core/tasks/MagiskInstallImpl.kt

@@ -239,6 +239,12 @@ abstract class MagiskInstallImpl : FlashResultListener {
     }
 
     private fun patchBoot(): Boolean {
+        var srcNand = ""
+        if ("[ -c $srcBoot ] && nanddump -f boot.img $srcBoot".sh().isSuccess) {
+            srcNand = srcBoot
+            srcBoot = File(installDir, "boot.img").path
+        }
+
         var isSigned = false
         try {
             SuFileInputStream(srcBoot).use {
@@ -258,6 +264,10 @@ abstract class MagiskInstallImpl : FlashResultListener {
             return false
         }
 
+        if (srcNand.isNotEmpty()) {
+            srcBoot = srcNand
+        }
+
         val job = Shell.sh(
                 "./magiskboot cleanup",
                 "mv bin/busybox busybox",