Setup Flutter desktop development environment manually

I choose the manual approach to make sure I know what is needed for building a flutter application.

Version of Flutter SDK is 1.20. Platform is Ubuntu 18.04. Here are the steps I took:

1. Download and unpack Flutter SDK.

2. Manually built and install cmake:

   • ./configure --prefix=.../bin/app/cmake-3.18>
   • make
   • make install

3. Manually built and install ninja:

   • python ./configure.py --bootstrap
   • mkdir -p .../bin/app/ninja-1.10/bin
   • cp ninja .../bin/app/ninja-1.10/bin/

4. Install clang and GTK-3 development files: sudo apt install clang pkg-config libgtk-3-dev.

   This will bring clang-6 into the box.

The environment can be verify by generate a empty project.