fetch: don't flag fs modification

Library/Homebrew/cmd/fetch.rb

@@ -32,6 +32,7 @@ module Homebrew
   def fetch_bottle? f
     return true if ARGV.force_bottle? && f.bottle
     return false unless f.bottle && f.pour_bottle?
+    return false if ARGV.build_from_source? || ARGV.build_bottle?
     if f.file_modified?
       filename = f.path.to_s.gsub("#{HOMEBREW_PREFIX}/", "")
       opoo "Formula file is modified!"
@@ -39,7 +40,6 @@ module Homebrew
       puts "To fetch the bottle instead, run with --force-bottle"
       return false
     end
-    return false if ARGV.build_from_source? || ARGV.build_bottle?
     return false unless f.bottle.compatible_cellar?
     return true
   end