#1406 Add documentation about set up of a macOS runner.

Documentation/ContinuousIntegration/Internal/SetUpmacOSVM.md

+<!-- toc -->
+
+
+# Install Miniconda environment
+
+
+````
+curl -O https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh
+bash Miniconda3-latest-MacOSX-x86_64.sh
+conda update conda
+conda create -n Python3  python=3
+conda activate Python3
+conda install six
+python -m pip install distro
+````
+
+# Install third party libraries
+
+````
+git clone https://gitlab.inria.fr/MoReFEM/ThirdPartyCompilationFactory.git
+````
+
+Edit morefem_macos_clang.py:
+
+````
+    target_directory = "/Volumes/Data/ci/opt/clang_{}".format(mode)
+    python = "/Users/ci/miniconda3/bin/python"
+````
+
+In Conda environment Python3:
+
+````    
+python morefem_macos_clang.py
+````
+
+# Install gitlab-runner
+
+## As an administrator:
+
+````
+sudo curl --output /usr/local/bin/gitlab-runner https://gitlab-runner-downloads.s3.amazonaws.com/latest/binaries/gitlab-runner-darwin-amd64
+
+sudo chmod +x /usr/local/bin/gitlab-runner
+````
+
+## As CI user:
+
+````
+gitlab-runner register
+````
+
+Then choose:
+
+- Please enter the gitlab-ci coordinator URL (e.g. https://gitlab.com/):
+
+    Copy/paste password the choice on ![Gitlab page](../Images/RunnerCredential.png).
+    
+- Please enter the gitlab-ci token for this runner:
+
+    The token given in Runner page (see image above).
+    
+- Please enter the gitlab-ci description for this runner:
+
+    You may just repeat the name of the machine... or really put whatever you want (you may change it afterwards anyway).
+    
+- Please enter the gitlab-ci tags for this runner (comma separated):
+    
+    Put the tags for the runner you want to set up, e.g. "macos,debug,shared"
+    
+- Please enter the executor:
+
+    Choose _shell_.
+    
+
+The runner should now appear in gitlab, but possibly with a grey dot instead of a green one. In this case, type:
+
+````
+gitlab-runner --debug run 
+````
+
+which should make the dot green within a minute.
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