Add downstream project build testing

scripts/read-cargo-variable.sh

@@ -0,0 +1,14 @@
+# source this file
+
+readCargoVariable() {
+  declare variable="$1"
+  declare Cargo_toml="$2"
+
+  while read -r name equals value _; do
+    if [[ $name = "$variable" && $equals = = ]]; then
+      echo "${value//\"/}"
+      return
+    fi
+  done < <(cat "$Cargo_toml")
+  echo "Unable to locate $variable in $Cargo_toml" 1>&2
+}