Check if the file is writable even while QT_BOOTSTRAPPED

QConfFile::isWritable() has the extra effect that it will try and
create the path where the file should be if it does not already
exist. So this cannot be omitted as 'qmake -set' may be used in a
situation where the path does not yet exist.

Change-Id: I0113644259f78d090a0687c44cf60d400be9c859
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

src/corelib/io/qsettings.cpp

@@ -1383,13 +1383,17 @@ void QConfFileSettingsPrivate::syncConfFile(int confFileNo)
         Concurrent read and write are not a problem because the writing operation is atomic.
     */
     QLockFile lockFile(confFile->name + QLatin1String(".lock"));
+#endif
     if (!readOnly) {
-        if (!confFile->isWritable() || !lockFile.lock() ) {
+        if (!confFile->isWritable()
+#ifndef QT_BOOTSTRAPPED
+            || !lockFile.lock()
+#endif
+            ) {
             setStatus(QSettings::AccessError);
             return;
         }
     }
-#endif
 
     /*
         We hold the lock. Let's reread the file if it has changed