Make fix objc build problem

gRPC-Core.podspec

@@ -89,6 +89,7 @@ Pod::Spec.new do |s|
 
   s.default_subspecs = 'Interface', 'Implementation'
   s.compiler_flags = '-DGRPC_ARES=0'
+  s.libraries = 'c++'
 
   # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
   # sources and private headers in other directories outside `include/`. Cocoapods' linter doesn't

src/core/ext/transport/chttp2/transport/flow_control.cc

@@ -165,7 +165,7 @@ TransportFlowControl::TransportFlowControl(grpc_exec_ctx* exec_ctx,
 
 uint32_t TransportFlowControl::MaybeSendUpdate(bool writing_anyway) {
   FlowControlTrace trace("t updt sent", this, nullptr);
-  const uint32_t target_announced_window = target_window();
+  const uint32_t target_announced_window = (const uint32_t)target_window();
   if ((writing_anyway || announced_window_ <= target_announced_window / 2) &&
       announced_window_ != target_announced_window) {
     const uint32_t announce = (uint32_t)GPR_CLAMP(

templates/gRPC-Core.podspec.template

@@ -116,6 +116,7 @@
 
     s.default_subspecs = 'Interface', 'Implementation'
     s.compiler_flags = '-DGRPC_ARES=0'
+    s.libraries = 'c++'
 
     # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
     # sources and private headers in other directories outside `include/`. Cocoapods' linter doesn't