LibCore: All BSDs need sig_t instead of sighandler_t

Userland/Libraries/LibCore/System.cpp

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

Userland/Libraries/LibCore/System.h

@@ -93,7 +93,7 @@ ErrorOr<int> accept4(int sockfd, struct sockaddr*, socklen_t*, int flags);
 #endif
 
 ErrorOr<void> sigaction(int signal, struct sigaction const* action, struct sigaction* old_action);
-#if defined(AK_OS_MACOS) || defined(AK_OS_OPENBSD) || defined(AK_OS_FREEBSD)
+#if defined(AK_OS_BSD_GENERIC)
 ErrorOr<sig_t> signal(int signal, sig_t handler);
 #else
 ErrorOr<sighandler_t> signal(int signal, sighandler_t handler);