Backend: introduce Android version check

- checks the supported.versions prop in anykernel.sh and matches against it to prevent users flashing incorrect kernels for ROM versions
- supported.versions can be a list, e.g. "7.1.2, 8.0, 8.1" or a range, e.g. "8.1 - 9" of versions in the correct formatting for that Android version in ro.build.version.release in /system/build.prop

META-INF/com/google/android/update-binary

@@ -1,5 +1,5 @@
 #!/sbin/sh
-# AnyKernel2 Backend
+# AnyKernel2 Backend (DO NOT CHANGE)
 # osm0sis @ xda-developers
 
 OUTFD=/proc/self/fd/$2;
@@ -120,11 +120,38 @@ if [ "$(file_getprop anykernel.sh do.devicecheck)" == 1 ]; then
     fi;
   done;
   ui_print " ";
-  if [ "$match" != 1 ]; then
+  if [ ! "$match" ]; then
     abort "Unsupported device. Aborting...";
   fi;
 fi;
 
+supported_ver="$(file_getprop anykernel.sh supported.versions | $bb tr -d '[:space:]')";
+if [ "$supported_ver" ]; then
+  ui_print "Checking Android version...";
+  android_ver="$(file_getprop /system/build.prop ro.build.version.release)";
+  if [ "$(echo $supported_ver | $bb grep -)" ]; then
+    lo_ver=$(echo $supported_ver | $bb cut -d- -f1);
+    hi_ver=$(echo $supported_ver | $bb cut -d- -f2);
+    if [ "$(echo -e "$hi_ver\n$lo_ver\n$android_ver" | $bb sort -g | $bb grep -n "$android_ver" | $bb grep '^2:')" ]; then
+      supported=1;
+    fi;
+  else
+    for ver in $(echo $supported_ver | $bb sed 's;,; ;g'); do
+      if [ "$ver" == "$android_ver" ]; then
+        supported=1;
+        break;
+      fi;
+    done;
+  fi;
+  if [ "$supported" ]; then
+    ui_print "$android_ver";
+    ui_print " ";
+  else
+    ui_print " ";
+    abort "Unsupported Android version. Aborting...";
+  fi;
+fi;
+
 ui_print "Installing...";
 for i in $($bb --list); do
   $bb ln -s $bb bin/$i;