Fix ObjC demo build: add -fobjc-arc flag to clang command

GCDAsyncSocket.m uses __weak references throughout which require
Automatic Reference Counting (ARC) to be enabled.

Co-authored-by: dustturtle <2305214+dustturtle@users.noreply.github.com>

Author: Copilot

.github/workflows/demo.yml

@@ -32,7 +32,7 @@ jobs:
 
       - name: Build ObjC Demo
         run: |
-          clang -framework Foundation -framework Network \
+          clang -fobjc-arc -framework Foundation -framework Network \
                 -I ObjC/NWAsyncSocketObjC/include \
                 ObjC/NWAsyncSocketObjC/NWStreamBuffer.m \
                 ObjC/NWAsyncSocketObjC/NWSSEParser.m \