Build: Do not strip .md extension from absolute URLs (#7222)

Makefile.js

@@ -658,8 +658,8 @@ target.gensite = function(prereleaseVersion) {
                 text = "---\ntitle: " + title + "\nlayout: doc\n---\n<!-- Note: No pull requests accepted for this file. See README.md in the root directory for details. -->\n\n" + text;
             }
 
-            // 6. Remove .md extension for links and change README to empty string
-            text = text.replace(/\.md(.*?\))/g, ")").replace("README.html", "");
+            // 6. Remove .md extension for relative links and change README to empty string
+            text = text.replace(/\((?!https?:\/\/)(.*?)\.md.*?\)/g, "($1)").replace("README.html", "");
 
             // 7. Check if there's a trailing white line at the end of the file, if there isn't one, add it
             if (!/\n$/.test(text)) {