GCC: detect compiler setting in C locale

Run detection of GCC compiler settings using the C locale. This
should fix detection of some settings in non english locales.

Task-number: QTCREATORBUG-5637
Change-Id: I3ea74ce5374fb03ea0cd43566ee302c635e02cd4
Reviewed-on: http://codereview.qt.nokia.com/2387Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>

src/plugins/projectexplorer/gcctoolchain.cpp

@@ -70,7 +70,12 @@ static QByteArray runGcc(const QString &gcc, const QStringList &arguments, const
         return QByteArray();
 
     QProcess cpp;
-    cpp.setEnvironment(env);
+    // Force locale: This function is used only to detect settings inside the tool chain, so this is save.
+    QStringList environment(env);
+    environment.append(QLatin1String("LC_ALL"));
+    environment.append(QLatin1String("C"));
+
+    cpp.setEnvironment(environment);
     cpp.start(gcc, arguments);
     if (!cpp.waitForStarted()) {
         qWarning("%s: Cannot start '%s': %s", Q_FUNC_INFO, qPrintable(gcc),