Fix two mistakes in art script rewrite.

Fix typo and mimic ART behavior for having just one -cp.

Test: art
Change-Id: Ic7c566f3dd29d1cad4c130e81cb7e7f609b5b1d1
diff --git a/tools/art b/tools/art
index 23eb23b..7bd4c54 100644
--- a/tools/art
+++ b/tools/art
@@ -229,11 +229,14 @@
         shift
         ;;
       -Ximage:*)
-        DEX2OAT_BOOTIMAGE=$1
+        DEX2OAT_BOOT_IMAGE=$1
         # Remove '-Ximage:' from the argument.
         DEX2OAT_BOOT_IMAGE=${DEX2OAT_BOOT_IMAGE##-Ximage:}
         ;;
       -cp)
+        # Reset any previously parsed classpath, just like dalvikvm
+        # only supports one -cp argument.
+        DEX2OAT_CLASSPATH=()
         # TODO: support -classpath and CLASSPATH
         local oifs=$IFS
         IFS=':'