OS X: Improve QLibraryInfo app bundle testing.

QLibraryInfo::location() paths are relative to
"myapp.app/Contents/" when the application has a
bundle and relative to the executable when not.

However CFBundleGetMainBundle() can and will return
a valid CFBundleRef even if the application is built
as a standalone executable.

Add a test that verifies that the path constructed
with "/Contents" exists on disk. Fall back to the
non-bundle code path if it doesn't.

This bug was hit in cases where a qt.conf file was
present side-by-side with the app binary, for example
in qtbase/bin.

Task-number: QTBUG-38039
Change-Id: Id993599208fe94fff283c725778f8ad47b610ba7
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

src/corelib/global/qlibraryinfo.cpp

@@ -498,7 +498,9 @@ QLibraryInfo::rawLocation(LibraryLocation loc, PathGroup group)
                     if (urlRef) {
                         QCFString path = CFURLCopyFileSystemPath(urlRef, kCFURLPOSIXPathStyle);
 #ifdef Q_OS_MACX
-                        return QDir::cleanPath(QString(path) + QLatin1String("/Contents/") + ret);
+                        QString bundleContentsDir = QString(path) + QLatin1String("/Contents/");
+                        if (QDir(bundleContentsDir).exists())
+                            return QDir::cleanPath(bundleContentsDir + ret);
 #else
                         return QDir::cleanPath(QString(path) + QLatin1Char('/') + ret); // iOS
 #endif