/etc/mtab not exists on OpenBSD

Index: src/solid/devices/backends/fstab/fstabwatcher.cpp
--- src/solid/devices/backends/fstab/fstabwatcher.cpp.orig
+++ src/solid/devices/backends/fstab/fstabwatcher.cpp
@@ -66,6 +66,7 @@ FstabWatcher::FstabWatcher()
     m_isRoutineInstalled = false;
     m_fileSystemWatcher = new QFileSystemWatcher(this);
 
+#ifndef Q_OS_OPENBSD
     m_mtabFile = new QFile(s_mtabFile, this);
     if (m_mtabFile && m_mtabFile->symLinkTarget().startsWith(QLatin1String("/proc/")) && m_mtabFile->open(QIODevice::ReadOnly)) {
         m_socketNotifier = new QSocketNotifier(m_mtabFile->handle(), QSocketNotifier::Exception, this);
@@ -73,6 +74,7 @@ FstabWatcher::FstabWatcher()
     } else {
         m_fileSystemWatcher->addPath(s_mtabFile);
     }
+#endif
 
     m_fileSystemWatcher->addPath(s_fstabPath);
     connect(m_fileSystemWatcher, &QFileSystemWatcher::directoryChanged, this, [this](const QString &) {
