LibCore: Use SIG_TYP instead of sig_t for signals on Solaris

Author: https://github.com/ghost
Commit: 50e663f561
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.cpp

@@ -330,7 +330,9 @@ ErrorOr<void> sigaction(int signal, struct sigaction const* action, struct sigac
     return {};
 }
 
-#if defined(AK_OS_BSD_GENERIC)
+#if defined(AK_OS_SOLARIS)
+ErrorOr<SIG_TYP> signal(int signal, SIG_TYP handler)
+#elif defined(AK_OS_BSD_GENERIC)
 ErrorOr<sig_t> signal(int signal, sig_t handler)
 #else
 ErrorOr<sighandler_t> signal(int signal, sighandler_t handler)