Fix the g++ build.

src/IceTargetLoweringX8664Traits.h

Index: src/IceTargetLoweringX8664Traits.h
diff --git a/src/IceTargetLoweringX8664Traits.h b/src/IceTargetLoweringX8664Traits.h
index 314416c565a1b94f85d21218eb62bca7e4391dc8..bab08a181c41f2908ed3481f6741953c4b36db0a 100644
--- a/src/IceTargetLoweringX8664Traits.h
+++ b/src/IceTargetLoweringX8664Traits.h
@@ -501,17 +501,17 @@ public:
 
     static constexpr struct {
       uint16_t Val;
-      int Is64 : 1;
-      int Is32 : 1;
-      int Is16 : 1;
-      int Is8 : 1;
-      int IsXmm : 1;
-      int Is64To8 : 1;
-      int Is32To8 : 1;
-      int Is16To8 : 1;
-      int IsTrunc8Rcvr : 1;
-      int IsAhRcvr : 1;
-      int Scratch : 1;
+      unsigned Is64 : 1;
+      unsigned Is32 : 1;
+      unsigned Is16 : 1;
+      unsigned Is8 : 1;
+      unsigned IsXmm : 1;
+      unsigned Is64To8 : 1;
+      unsigned Is32To8 : 1;
+      unsigned Is16To8 : 1;
+      unsigned IsTrunc8Rcvr : 1;
+      unsigned IsAhRcvr : 1;
+      unsigned Scratch : 1;
 #define NUM_ALIASES_BITS 2
       SizeT NumAliases : (NUM_ALIASES_BITS + 1);
       uint16_t Aliases[1 << NUM_ALIASES_BITS];