Make mkdir wrapper use mkdir_p to create intermediate directories

Library/Homebrew/extend/fileutils.rb

@@ -88,7 +88,7 @@ module FileUtils
 
   # A version of mkdir that also changes to that folder in a block.
   def mkdir(name, &_block)
-    old_mkdir(name)
+    mkdir_p(name)
     if block_given?
       chdir name do
         yield

Library/Homebrew/test/test_pathname.rb

@@ -257,4 +257,11 @@ class PathnameInstallTests < Homebrew::TestCase
     @dst.install_symlink "foo" => "bar"
     assert_equal Pathname.new("foo"), (@dst/"bar").readlink
   end
+
+  def test_mkdir_creates_intermediate_directories
+    mkdir @dst/"foo/bar/baz" do
+      assert_predicate @dst/"foo/bar/baz", :exist?, "foo/bar/baz was not created"
+      assert_predicate @dst/"foo/bar/baz", :directory?, "foo/bar/baz was not a directory structure"
+    end
+  end
 end