fix(examples): scope macOS frameworks to darwin in cgo LDFLAGS

The go-demo cgo LDFLAGS hardcoded `-framework CoreFoundation
-framework Security`, which only exist on macOS. On the Linux CI
runner gcc rejects `-framework`, breaking the examples build. Move
those flags to a `#cgo darwin LDFLAGS` line so Linux links with just
the portable flags while macOS still pulls the frameworks the Rust
staticlib needs transitively.

Signed-off-by: Frederico Araujo <frederico.araujo@ibm.com>

Author: araujof

examples/go-demo/cmd/cmf-demo/main.go

@@ -25,7 +25,11 @@
 package main
 
 /*
-#cgo LDFLAGS: -L${SRCDIR}/../../../../target/release -lcpex_demo_ffi -lm -ldl -lpthread -framework CoreFoundation -framework Security
+#cgo LDFLAGS: -L${SRCDIR}/../../../../target/release -lcpex_demo_ffi -lm -ldl -lpthread
+// CoreFoundation/Security are macOS-only; the Rust staticlib pulls them
+// in transitively there. Linux gcc rejects `-framework`, so scope these
+// to darwin and leave Linux with the portable flags above.
+#cgo darwin LDFLAGS: -framework CoreFoundation -framework Security
 #include <stdlib.h>
 
 int cpex_demo_register_factories(void* mgr);

examples/go-demo/main.go

@@ -23,7 +23,11 @@
 package main
 
 /*
-#cgo LDFLAGS: -L${SRCDIR}/../../target/release -lcpex_demo_ffi -lm -ldl -lpthread -framework CoreFoundation -framework Security
+#cgo LDFLAGS: -L${SRCDIR}/../../target/release -lcpex_demo_ffi -lm -ldl -lpthread
+// CoreFoundation/Security are macOS-only; the Rust staticlib pulls them
+// in transitively there. Linux gcc rejects `-framework`, so scope these
+// to darwin and leave Linux with the portable flags above.
+#cgo darwin LDFLAGS: -framework CoreFoundation -framework Security
 #include <stdlib.h>
 
 int cpex_demo_register_factories(void* mgr);