Added Rust crates script

Necessary to implement the installation of Rust and associated crates
which can be used by downstream configurations. This functionality was
originally part of the macOS Configuration project but has been moved
here to provide a common foundation in which to build upon.

bin/install_rust_crates

@@ -0,0 +1,17 @@
+#! /usr/bin/env bash
+
+# Installs Rust crates.
+
+set -o nounset
+set -o errexit
+set -o pipefail
+IFS=$'\n\t'
+
+SCRIPT_PATH="$MAC_OS_CONFIG_PATH/bin/install_rust_crates"
+
+if [[ -x "$SCRIPT_PATH" ]]; then
+  install_rust
+  "$SCRIPT_PATH"
+else
+  printf "WARNING: Rust crates install script does not exist or is not executable.\n"
+fi

bin/run

@@ -39,6 +39,7 @@ while true; do
     printf "     m:  Install Mac App Store software.\n"
     printf "     a:  Install application software.\n"
     printf "     x:  Install application software extensions.\n"
+    printf "    rc:  Install Rust crates.\n"
     printf "     d:  Apply default settings.\n"
     printf "     s:  Setup installed software.\n"
     printf "     i:  Install everything (i.e. executes all install options).\n"