Fix factory installer for ARM platforms

factory_reset.sh

Index: factory_reset.sh
diff --git a/factory_reset.sh b/factory_reset.sh
index 3d5e66c16eaddf2bc4a204366b69f278006e80fe..a507904d59dbfc53e1fa451376856f8b8404acf5 100644
--- a/factory_reset.sh
+++ b/factory_reset.sh
@@ -9,12 +9,26 @@
 # put the system back into factory fresh/shippable state.
 echo "Factory reset"
 
-# TODO: How do we know what this is for the general case?
-if [ -b /dev/sda ]; then
+# TODO(crosbug:10680): replace arch detection with crossystem?
+if uname -m | grep -q "^i.86\$"; then
+  ARCH="INTEL"
+elif [ $(uname -m ) = "x86_64" ]; then
+  ARCH="INTEL"
+elif [ $(uname -m ) = "armv7l" ]; then
+  ARCH="ARM"
+else
+  echo "Failed to auto detect architecture"
+  exit 1
+fi
+
+if [ "$ARCH" = "INTEL" ]; then
   STATE_DEV="/dev/sda1"
-elif [ -b /dev/mmcblk0 ]; then
-  STATE_DEV="/dev/mmcblk01"
+elif [ "$ARCH" = "ARM" ]; then
+  STATE_DEV="/dev/mmcblk0p1"
 else
+  STATE_DEV=""
+fi
+if [ ! -b "$STATE_DEV" ]; then
   echo "Failed to find root SSD."
   exit 1
 fi