use negative mask

the test should be for _invalid_ bits; as it's written,
it tests for valid bits

Change-Id: Id5e42e865449a7877fe58aca9fb47675fa7452c9
diff --git a/cmds/installd/commands.cpp b/cmds/installd/commands.cpp
index d3efb7c..757290f 100644
--- a/cmds/installd/commands.cpp
+++ b/cmds/installd/commands.cpp
@@ -1066,7 +1066,7 @@
     bool boot_complete = (dexopt_flags & DEXOPT_BOOTCOMPLETE) != 0;
     bool use_jit = (dexopt_flags & DEXOPT_USEJIT) != 0;
 
-    if ((dexopt_flags & DEXOPT_MASK) != 0) {
+    if ((dexopt_flags & ~DEXOPT_MASK) != 0) {
         LOG_FATAL("dexopt flags contains unknown fields\n");
     }