Set CLOEXEC flag on sockets

If SOCK_CLOEXEC exists, then set the flag on socket creation.

Otherwise, use fcntl() (or SetHandleInformation() on Windows) to set the
flag afterwards.

This avoids the sockets to be inherited in child processes.

Refs #2783 <https://github.com/Genymobile/scrcpy/pull/2783>

app/meson.build

@@ -149,6 +149,9 @@ foreach f : check_functions
   endif
 endforeach
 
+conf.set('HAVE_SOCK_CLOEXEC', host_machine.system() != 'windows' and
+                              cc.has_header_symbol('sys/socket.h', 'SOCK_CLOEXEC'))
+
 # the version, updated on release
 conf.set_quoted('SCRCPY_VERSION', meson.project_version())