Build extensions in verbose mode by default.

Index: ext/extmk.rb
--- ext/extmk.rb.orig
+++ ext/extmk.rb
@@ -712,7 +712,7 @@ exts.map! {|d| "#{ext_prefix}/#{d}/."}
 FileUtils.makedirs(File.dirname($command_output))
 begin
   atomic_write_open($command_output) do |mf|
-    mf.puts "V = 0"
+    mf.puts "V = 1"
     mf.puts "V0 = $(V:0=)"
     mf.puts "Q1 = $(V:1=)"
     mf.puts "Q = $(Q1:0=@)"