main: ignore SIGPIPE globally. (WayfireWM#2096)

By default, writing to a pipe that has been closed terminates the
program with SIGPIPE. Ignoring SIGPIPE results in the syscall
failing with EPIPE instead.

This generally prevents crashing on IPCs. One crash I found is in
write_selection_property_to_wl_client when using xpra to run
remote apps. If xpra updates the selection too often, wayfire
crashes with SIGPIPE. But this probably prevents other crashes in
general. It also matches what other compositors do, e.g., sway
also globally ignores SIGPIPE to prevent crashes caused by IPCs.

src/main.cpp

@@ -311,6 +311,9 @@ int main(int argc, char *argv[])
         }
     }
 
+    /* Don't crash on SIGPIPE, e.g., when doing IPC to a client whose fd has been closed. */
+    signal(SIGPIPE, SIG_IGN);
+
     wf::log::initialize_logging(std::cout, log_level, detect_color_mode());
 
     parse_extended_debugging(extended_debug_categories);