1 files changed, 6 insertions, 0 deletions
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 96696b1f3b..45bf90872d 100644
--- a/lib/mkmf.rb
+++ b/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)