Add scripts to simplify offline builds of docs and CMake

tools/offline/scripts/init_git_cache.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+if [ -z "${GITHUB_PROXY_DIR}" ]
+then
+    echo "Must set GITHUB_PROXY_DIR environment variable"
+    exit 1
+fi
+
+mkdir -p $GITHUB_PROXY_DIR
+cd $GITHUB_PROXY_DIR
+
+PROJECTS=(
+    akohlmey/sphinx-fortran
+    mathjax/MathJax
+)
+
+for project in ${PROJECTS[@]}
+do
+    GH_NAMESPACE=$(dirname $project)
+    GH_PROJECT=$(basename $project)
+    mkdir -p $GH_NAMESPACE
+    git clone --bare https://github.com/$GH_NAMESPACE/$GH_PROJECT.git $GH_NAMESPACE/$GH_PROJECT.git
+done