IPC: handle EMFILE as an OutOfResources error

In QSystemSemaphore (QSharedMemory already has it).

When running tst_QSharedMemory::useTooMuchMemory on 64-bit Linux with
POSIX IPC, we run out of file descriptors before we run out of memory.

Change-Id: I12a088d1ae424825abd3fffd171d6f34c002b5a1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/ipc/qsystemsemaphore.cpp

@@ -342,6 +342,7 @@ void QSystemSemaphorePrivate::setUnixErrorString(QLatin1StringView function)
         break;
     case ERANGE:
     case ENOSPC:
+    case EMFILE:
         errorString = QSystemSemaphore::tr("%1: out of resources").arg(function);
         error = QSystemSemaphore::OutOfResources;
         break;