LibCore: Implement socket credentials for Solaris

Author: https://github.com/ghost
Commit: cdd1c8d0d9
Pull-request: https://github.com/SerenityOS/serenity/pull/17623
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/elcuco
Reviewed-by: https://github.com/kleinesfilmroellchen ✅
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibCore/System.h

@@ -37,6 +37,7 @@
 
 #ifdef AK_OS_SOLARIS
 #    include <sys/filio.h>
+#    include <ucred.h>
 #endif
 
 namespace Core::System {