Add clear_cache package (#4282)

packages/clear_cache.rb

+require 'package'
+
+class Clear_cache < Package
+  description 'Script to remove system cache files'
+  homepage 'https://github.com/skycocker/chromebrew/wiki/FAQ'
+  version '1.0'
+  compatibility 'all'
+  source_url 'file:///dev/null'
+  source_sha256 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
+
+  def self.build
+    system "cat << 'EOF' > clear-cache
+#!/bin/bash
+cd \$HOME
+SPACE_BEFORE=\$(du -s | cut -f1)
+SPACE_BEFORE_HUMAN=\$(du -hs | cut -f1)
+DIRS=\".cache Cache Application_Cache Code_Cache GCache GPUCache Service_Worker\"
+for D in \$DIRS; do
+  DIR=\$(echo \$D | sed \'s,_, ,\')
+  [ -d \"\$DIR\" ] && rm -rf \"\$DIR\"
+done
+SPACE_AFTER=\$(du -s | cut -f1)
+SPACE_AFTER_HUMAN=\$(du -hs | cut -f1)
+SPACE_RECOVERED=\$((\$SPACE_BEFORE-\$SPACE_AFTER))
+echo \"Space used before: \$SPACE_BEFORE_HUMAN\"
+echo \"Space used after: \$SPACE_AFTER_HUMAN\"
+echo \"Space recovered: \${SPACE_RECOVERED}KB\"
+EOF"
+  end
+
+  def self.install
+    system "install -Dm755 clear-cache #{CREW_DEST_PREFIX}/bin/clear-cache"
+  end
+
+  def self.postinstall
+    puts
+    puts "Type 'clear-cache' to remove system cache files.".lightblue
+    puts
+  end
+end