Fix compilation with GCC 5.2

src/compiler/ia32/code-generator-ia32.cc

Index: src/compiler/ia32/code-generator-ia32.cc
diff --git a/src/compiler/ia32/code-generator-ia32.cc b/src/compiler/ia32/code-generator-ia32.cc
index d67be6bff99d96cd43d443c7a01ad620d6eebef3..a1de0578a8c12964453e6ac26e78115d40cb3b21 100644
--- a/src/compiler/ia32/code-generator-ia32.cc
+++ b/src/compiler/ia32/code-generator-ia32.cc
@@ -1363,7 +1363,7 @@ void CodeGenerator::AssembleReturn() {
   }
   size_t pop_size = descriptor->StackParameterCount() * kPointerSize;
   // Might need ecx for scratch if pop_size is too big.
-  DCHECK_EQ(0, descriptor->CalleeSavedRegisters() & ecx.bit());
+  DCHECK_EQ(0u, descriptor->CalleeSavedRegisters() & ecx.bit());
   __ Ret(static_cast<int>(pop_size), ecx);
 }