test-bot: tap TapDependency recursively

Closes Homebrew/homebrew#43145.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/cmd/test-bot.rb

@@ -410,11 +410,15 @@ module Homebrew
       end
 
       begin
-        deps.each do |dep|
-          if dep.is_a?(TapDependency) && dep.tap
-            tap_dir = Homebrew.homebrew_git_repo dep.tap
-            test "brew", "tap", dep.tap unless tap_dir.directory?
+        formula.recursive_dependencies
+      rescue TapFormulaUnavailableError => e
+        raise if e.tap.installed?
+        safe_system "brew", "tap", e.tap.name
+        retry
       end
+
+      begin
+        deps.each do |dep|
           CompilerSelector.select_for(dep.to_formula)
         end
         CompilerSelector.select_for(formula)