making core tap install an in-process call

This helps fixes problems with fresh install on ARM Linux.
When brew is relaunched with filtered PATH, it is not able to
find user installed Ruby.

Library/Homebrew/tap.rb

@@ -800,7 +800,7 @@ class CoreTap < Tap
     # Tests override homebrew-core locations and we don't want to auto-tap in them.
     return if ENV["HOMEBREW_TESTS"]
 
-    safe_system HOMEBREW_BREW_FILE, "tap", instance.name
+    instance.install
   end
 
   def remote

Library/Homebrew/utils/tty.rb

@@ -87,7 +87,7 @@ module Tty
     CODES.each do |name, code|
       define_method(name) do
         @escape_sequence ||= []
-        @escape_sequence << code
+        @escape_sequence << code if @escape_sequence
         self
       end
     end