docs: adding warning to keep the source code in separate repo

documentation/best_practices/cmake.rst

@@ -7,6 +7,13 @@ Example of using CMake with Bitbake recipes.
 Please find the example here:
 `CMake Yocto Example <https://bitbucket.gad.local/projects/ICO/repos/coreos/browse/layers/meta-belden-coreos-demo/recipes-demo/cmake-demo/cmake-demo_0.1.bb>`_.
 
+.. warning::
+   This simple example has the code in the same repo as the recipe. However, it is recommended to have the code in a separate git repo.
+   To use remote git repo, it's necessary to have settings as follows:
+   
+   * SRC_URI = "git://github.com/<link to your repo>"
+   * S="${WORKDIR}/git
+
 
 BitBake recipe
 ===============