I just opened Android Studio and updated to the latest version Android Studio 2.1 Preview 3. I don't know where the problem is but when I try to build a new project some error occurs. Didn't have this problem with an older version of Android Studio and the reason that I updated it was because I thought I might be able to generate signed Apk's.
Here you have a screenshot I took from the Android Studio :
If you use an Android Studio project generated by the Introjucer, never change any build settings by clicking on such prompts in Android Studio, as this will often completely break the project. Manage all your build settings in the Introjucer.
Also, don't use Android Studio on Windows, this is unfortunately still quite flaky and buggy at the moment (not much we can do about that). If you want to develop for Android, I strongly suggest switching to Mac OS X or Ubuntu.
That being said, there seems to be some problems since the Android Studio 2.1 release, as other people reported similar things, I'll check it out as soon as I have the time.
I downloaded Ubuntu 14.04 LTS and I had the following errors:
1- ./Projucer: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by ./Projucer)
./Projucer: /usr/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by ./Projucer)
I managed to solve the first one from google.
2- ./Projucer: relocation error: ./Projucer: symbol _ZTVNSt7__cxx1115basic_stringbufIcSt11char_traitsIcESaIcEEE, version GLIBCXX_3.4.21 not defined in file libstdc++.so.6 with link time reference
I don't know how to solve the second one.
You suggested me to use Ubuntu and that's what I did.