Add -framework Security to fix linker error for sec_protocol_options_set_verify_block

The TLS verify block in connectToHost:onPort:withTimeout:error: uses
sec_protocol_options_set_verify_block from the Security framework,
which was not linked in the CI build command. Also updated build
instructions in main.m comment and README.md to include the required
-fobjc-arc, -framework Network, and -framework Security flags.

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 -fobjc-arc -framework Foundation -framework Network \
+          clang -fobjc-arc -framework Foundation -framework Network -framework Security \
                 -I ObjC/NWAsyncSocketObjC/include \
                 ObjC/NWAsyncSocketObjC/NWStreamBuffer.m \
                 ObjC/NWAsyncSocketObjC/NWSSEParser.m \

ObjC/ObjCDemo/main.m

@@ -13,7 +13,7 @@
 //    6. GCDAsyncSocket  — Server socket API (accept/listen)
 //
 //  Build (from repository root):
-//    clang -framework Foundation \
+//    clang -framework Foundation -framework Network -framework Security \
 //          -I ObjC/NWAsyncSocketObjC/include \
 //          ObjC/NWAsyncSocketObjC/NWStreamBuffer.m \
 //          ObjC/NWAsyncSocketObjC/NWSSEParser.m \

README.md

@@ -321,7 +321,7 @@ The demo menu lets you test each component individually or run all at once:
 Build the ObjC CLI demo on macOS:
 
 ```bash
-clang -framework Foundation \
+clang -fobjc-arc -framework Foundation -framework Network -framework Security \
       -I ObjC/NWAsyncSocketObjC/include \
       ObjC/NWAsyncSocketObjC/NWStreamBuffer.m \
       ObjC/NWAsyncSocketObjC/NWSSEParser.m \