Don't set $VERBOSE when building nonverbosely

Setting $VERBOSE in the environment makes the haskell-platform build
fall down, which is surely one of the odder bugs I've run into.

See Homebrew/homebrew#15164.

Library/Homebrew/formula.rb

@@ -529,7 +529,6 @@ protected
 
       rd, wr = IO.pipe
       pid = fork do
-        ENV['VERBOSE'] = '1' # helps with many tool's logging outputs
         rd.close
         $stdout.reopen wr
         $stderr.reopen wr