* lib/mkmf.rb (xsystem): expand macros like as make.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@15402 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/mkmf.rb

@@ -267,6 +267,12 @@ module Logging
 end
 
 def xsystem command
+  varpat = /\$\((\w+)\)|\$\{(\w+)\}/
+  if varpat =~ command
+    vars = Hash.new {|h, k| h[k] = ''; ENV[k]}
+    command = command.dup
+    nil while command.gsub!(varpat) {vars[$1||$2]}
+  end
   Logging::open do
     puts command.quote
     system(command)