Android: Don't let the user choose a stupid ANDROID_PACKAGE_SOURCE_DIR

On creating a AndroidManifest.xml we ask the user where to put the file,
which as a sideeffect also sets ANDROID_PACKAGE_DIR.

Since we copy everthing from ANDROID_PACKAGE_SOURCE_DIR into the build
directory, using the project's source directory is not desireable.

We now show a big error if the user tries that.

Task-number: QTCREATORBUG-11708
Change-Id: I7fade3efac0b7466cad8e83a92c2115d0a70c683
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

src/plugins/android/createandroidmanifestwizard.h

@@ -34,6 +34,7 @@
 
 QT_BEGIN_NAMESPACE
 class QComboBox;
+class QLabel;
 QT_END_NAMESPACE
 
 namespace ProjectExplorer { class Target; }
@@ -70,9 +71,16 @@ class ChooseDirectoryPage : public QWizardPage
     Q_OBJECT
 public:
     ChooseDirectoryPage(CreateAndroidManifestWizard *wizard);
+protected:
+    bool isComplete() const;
+private slots:
+    void checkPackageSourceDir();
 private:
     CreateAndroidManifestWizard *m_wizard;
     Utils::PathChooser *m_androidPackageSourceDir;
+    QLabel *m_sourceDirectoryWarning;
+    QLabel *m_warningIcon;
+    bool m_complete;
 };
 
 class CreateAndroidManifestWizard : public Utils::Wizard