audit: Escape interpolated string in regexp

This avoids issues with names containing special characters like e.g. [

Fixes #1431

Library/Homebrew/dev-cmd/audit.rb

@@ -741,7 +741,7 @@ class FormulaAuditor
     end
     bin_names.each do |name|
       ["system", "shell_output", "pipe_output"].each do |cmd|
-        if text =~ /(def test|test do).*#{cmd}[\(\s]+['"]#{name}[\s'"]/m
+        if text =~ /(def test|test do).*#{cmd}[\(\s]+['"]#{Regexp.escape name}[\s'"]/m
           problem %(fully scope test #{cmd} calls e.g. #{cmd} "\#{bin}/#{name}")
         end
       end