CrashReporter: fix deadlocks by making it mostly async-signal-safe (#5771)

`CrashReporter::createAndSaveCrash()` is not async-signal-safe,
resulting in random deadlocks/double-crashes during Hyprland crashes.
This changes the function to be (mostly) async-signal-safe.

src/Compositor.cpp

@@ -36,6 +36,14 @@ void handleUnrecoverableSignal(int sig) {
         return;
     }
 
+    // Kill the program if the crash-reporter is caught in a deadlock.
+    signal(SIGALRM, [](int _) {
+        char const* msg = "\nCrashReporter exceeded timeout, forcefully exiting\n";
+        write(2, msg, strlen(msg));
+        abort();
+    });
+    alarm(15);
+
     CrashReporter::createAndSaveCrash(sig);
 
     abort();