Disable Quick's GVN-based dead code elimination.

Quick's GVN/DCE seems to trouble the builds.

Bug: 20572509
Change-Id: I1e315b4eee4443f04c7cb2cef953d8e4eff619ce
diff --git a/compiler/dex/quick/quick_compiler.cc b/compiler/dex/quick/quick_compiler.cc
index 73cfe92..39eb117 100644
--- a/compiler/dex/quick/quick_compiler.cc
+++ b/compiler/dex/quick/quick_compiler.cc
@@ -575,7 +575,7 @@
   // (1 << kNullCheckElimination) |
   // (1 << kClassInitCheckElimination) |
   // (1 << kGlobalValueNumbering) |
-  // (1 << kGvnDeadCodeElimination) |
+  (1 << kGvnDeadCodeElimination) |
   // (1 << kLocalValueNumbering) |
   // (1 << kPromoteRegs) |
   // (1 << kTrackLiveTemps) |