message: add description to udate the submodules
diff: @@ -60,8 +60,18 @@ such as:
  * QEMU (`apt-get install qemu-system-x86`)
  +## Building HermitCore
  +
  +### Preliminary work
  +
  +To build HermitCore from source (without compiler), the repository with its submodules has to be cloned.
  -## CMake requirements
  +```bash
  +$ git clone git@github.com:RWTH-OS/HermitCore.git
  +$ cd HermitCore
  +$ git submodule init
  +$ git submodule update
  +```
  We require a fairly recent version of CMake (`3.7`) which is not yet present in
  most Linux distributions. We therefore provide a helper script that fetches the
  @@ -91,8 +101,9 @@ cmake-3.7.2-Linux-x86_64.tar.gz 100%[===================>] 29,26M 3,74
  So before you build HermitCore you have to source the `local-cmake.sh` script
  everytime you open a new terminal.
  +### Building the library perating systems and its examples
  -## Building HermitCore
  +To build HermitCore go to the directory with the source code, create a `build` directory and call `cmake` followed by `make`.
  ```bash
  $ mkdir build
  