Cache clojure dependencies

This speeds up builds that use the [Clojure CLI][clojure-cli] by
avoiding network calls to download dependencies.

When a repo has a `deps.edn` file, we assume it is a Clojure repo. We
cache its dependencies by caching the following files:

* `.m2` As a JVM language, most Clojure dependencies are stored in the
  global `.m2` directory.
* `.gitlibs` The Clojure CLI can also download dependencies directly
  from git repositories rather than from a package manager. It caches
  these downloads in the `.gitlibs` directory.
* `.cpcache` Clojure uses the `.cpcache` directory to avoid
  unnecessarily re-calculating the JVM classpath. Caching this directory
  won't prevent downloads, but does improve build time slightly.

Fixes #485.

[clojure-cli]: https://clojure.org/reference/deps_and_cli

run-build-functions.sh

@@ -612,6 +612,14 @@ install_dependencies() {
     fi
   fi
 
+  # Clojure CLI
+  if [ -f deps.edn ]
+  then
+    restore_home_cache ".m2" "maven dependencies"
+    restore_home_cache ".gitlibs" "clojure git dependencies"
+    restore_cwd_cache ".cpcache" "clojure classpath"
+  fi
+
   # Hugo
   if [ -n "$HUGO_VERSION" ]
   then
@@ -699,6 +707,7 @@ cache_artifacts() {
 
   cache_cwd_directory ".venv" "python virtualenv"
   cache_cwd_directory ".build" "swift build"
+  cache_cwd_directory ".cpcache" "clojure classpath"
   cache_cwd_directory ".netlify/plugins" "build plugins"
   cache_cwd_directory ".netlify/rust-functions-cache" "Rust functions"
 
@@ -713,6 +722,7 @@ cache_artifacts() {
   cache_home_directory ".emacs.d" "emacs cache"
   cache_home_directory ".m2" "maven dependencies"
   cache_home_directory ".boot" "boot dependencies"
+  cache_home_directory ".gitlibs" "clojure git dependencies"
   cache_home_directory ".composer" "composer dependencies"
   cache_home_directory ".homebrew-cache", "homebrew cache"
   cache_home_directory ".rustup" "rust rustup cache"
@@ -934,4 +944,3 @@ install_go() {
   fi
 
 }
-