create a .qmake.cache for the lupdate tests

mac mkspecs are really noisy without it now, which makes the tests fail.

Change-Id: I6b4900c51d0b8aedd9309482a30055e48c3b9f69
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

tests/auto/linguist/lupdate/.gitignore

@@ -2,3 +2,4 @@ tst_lupdate
 testdata/*/*.ts
 testdata/*/*/*.ts
 testdata/*/*/*/*.ts
+testdata/good/*/.qmake.cache

tests/auto/linguist/lupdate/tst_lupdate.cpp

@@ -280,6 +280,10 @@ void tst_lupdate::good()
             QVERIFY2(QFile::copy(beforetsfile, genTs), qPrintable(beforetsfile));
     }
 
+    file.setFileName(workDir + QStringLiteral("/.qmake.cache"));
+    QVERIFY(file.open(QIODevice::WriteOnly));
+    file.close();
+
     if (lupdatecmd.isEmpty())
         lupdatecmd = QLatin1String("project.pro");
     lupdatecmd.prepend("-silent ");