Update of README file

Author: jctophefabre

README.md

@@ -1,3 +1,42 @@
 # OpenFLUID LandR library
 
-**WARNING: The OpenFLUID LandR library sources are currently being migrated. They cannot currently be built correctly and should not be used.**
+The OpenFLUID LandR (`openfluid-landr`) library is a C++ library for topological processing of geometries, focused on digital representation of landscapes geometries.  
+It was formerly part of the [OpenFLUID software sources](https://github.com/OpenFLUID).
+
+
+The `openfluid-landr` library relies on the following sofware
+
+* [OpenFLUID framework](https://openfluid-project.org)
+* [GEOS library](https://trac.osgeo.org/geos)
+* [Boost library](https://www.boost.org/)
+
+:warning: **Due to major breaking changes in GEOS dependency, the openfluid-landr source code is not currently stable and does not compile as is**
+
+
+## Build
+
+_NOTE: The build of openfluid-landr library has only been tested on Linux systems (Ubuntu 18.04 and 20.04)_  
+
+
+It requires the [GCC compiler](https://gcc.gnu.org/) compiler and the [CMake configuration tool](https://cmake.org/) to be built.  
+
+* Create the build directory in the sources directory
+```txt
+mkdir _build
+cd _build
+```
+
+* Configure the build
+```txt
+cmake ..
+```
+
+* Execute the build
+```txt
+make
+```
+
+* Run the tests
+```txt
+ctest
+```