Fix ARM build for gcc-4.6

src/arm/stub-cache-arm.cc

Index: src/arm/stub-cache-arm.cc
diff --git a/src/arm/stub-cache-arm.cc b/src/arm/stub-cache-arm.cc
index 1767b9d5b2513bde3f0fbef4e4c7528eabe28eaf..16e64684226661938669d0b16f95c62c045047cd 100644
--- a/src/arm/stub-cache-arm.cc
+++ b/src/arm/stub-cache-arm.cc
@@ -1183,9 +1183,8 @@ void StubCompiler::GenerateLoadConstant(JSObject* object,
   __ JumpIfSmi(receiver, miss);
 
   // Check that the maps haven't changed.
-  Register reg =
-      CheckPrototypes(object, receiver, holder,
-                      scratch1, scratch2, scratch3, name, miss);
+  CheckPrototypes(object, receiver, holder, scratch1, scratch2, scratch3, name,
+                  miss);
 
   // Return the constant value.
   __ mov(r0, Operand(Handle<Object>(value)));