Fix gcc-4.8

c++/src/capnp/capability.c++

@@ -121,7 +121,7 @@ struct LocalCapDescriptor {
 };
 
 template <>
-StructSize structSize<LocalCapDescriptor>() {
+constexpr StructSize structSize<LocalCapDescriptor>() {
   return StructSize(1 * WORDS, 0 * POINTERS, FieldSize::FOUR_BYTES);
 }
 

c++/src/kj/async.c++

@@ -352,7 +352,7 @@ ForkBranchBase::ForkBranchBase(Own<const ForkHubBase>&& hubParam): hub(kj::mv(hu
   }
 }
 
-ForkBranchBase::~ForkBranchBase() {
+ForkBranchBase::~ForkBranchBase() noexcept(false) {
   if (prevPtr != nullptr) {
     // Remove from hub's linked list of branches.
     auto lock = hub->branchList.lockExclusive();

c++/src/kj/async.h

@@ -975,7 +975,7 @@ class ForkHubBase;
 class ForkBranchBase: public PromiseNode {
 public:
   ForkBranchBase(Own<const ForkHubBase>&& hub);
-  ~ForkBranchBase();
+  ~ForkBranchBase() noexcept(false);
 
   void hubReady() noexcept;
   // Called by the hub to indicate that it is ready.