Use pacman cache of the main MSYS2 environment

recipes/msys2/50-install-components.rake

@@ -1,11 +1,15 @@
-# Use one file out of many to indicate installation of devtools
-self.devtools = File.join(self.sandboxdir, "/var/lib/pacman/local/mingw-w64-x86_64-gcc-6.3.0-3/desc")
+self.devtools = File.join(thisdir, "devtools_installed")
+# Use the cache of our main MSYS2 environment for package install
+cachedir = File.join(Build.msys2_installation.msys_path, "/var/cache/pacman/pkg")
 
 file self.devtools => [self.sandboxdir] do |t|
   msys = RubyInstaller::Build::Msys2Installation.new(self.sandboxdir)
   msys.with_msys_apps_enabled do
-    sh "sh -lc 'pacman -Syu --noconfirm' # Update the package database and core system packages"
-    sh "sh -lc 'pacman -Su --noconfirm' # Update the rest"
+    # Update the package database and core system packages
+    sh "sh", "-lc", "pacman --cachedir=`cygpath -u #{cachedir.inspect}` -Syu --noconfirm"
+    # Update the rest
+    sh "sh", "-lc", "pacman --cachedir=`cygpath -u #{cachedir.inspect}` -Su --noconfirm"
+    # Install the development tools
     RubyInstaller::Build::ComponentsInstaller.new.install(%w[dev_tools])
   end
   touch self.devtools