8176509: Use pandoc for converting build readme to html

Reviewed-by: erikj

README

@@ -1,40 +1,10 @@
-README:
-  This file should be located at the top of the OpenJDK Mercurial root
-  repository. A full OpenJDK repository set (forest) should also include
-  the following 7 nested repositories:
-    "jdk", "hotspot", "langtools", "nashorn", "corba", "jaxws"  and "jaxp".
+Welcome to OpenJDK!
+===================
 
-  The root repository can be obtained with something like:
-    hg clone http://hg.openjdk.java.net/jdk9/jdk9 openjdk9
+For information about building OpenJDK, including how to fully retrieve all
+source code, please see either of these:
 
-  You can run the get_source.sh script located in the root repository to get
-  the other needed repositories:
-    cd openjdk9 && sh ./get_source.sh
+  * common/doc/building.html   (html version)
+  * common/doc/building.md     (markdown version)
 
-  People unfamiliar with Mercurial should read the first few chapters of
-  the Mercurial book: http://hgbook.red-bean.com/read/
-
-  See http://openjdk.java.net/ for more information about OpenJDK.
-
-Simple Build Instructions:
-
-  0. Get the necessary system software/packages installed on your system, see
-     http://hg.openjdk.java.net/jdk9/jdk9/raw-file/tip/README-builds.html
-
-  1. If you don't have a jdk8 or newer jdk, download and install it from
-     http://java.sun.com/javase/downloads/index.jsp
-     Add the /bin directory of this installation to your PATH environment
-     variable.
-
-  2. Configure the build:
-       bash ./configure
-
-  3. Build the OpenJDK:
-       make all
-     The resulting JDK image should be found in build/*/images/jdk
-
-where make is GNU make 3.81 or newer, /usr/bin/make on Linux usually
-is 3.81 or newer. Note that on Solaris, GNU make is called "gmake".
-
-Complete details are available in the file:
-     http://hg.openjdk.java.net/jdk9/jdk9/raw-file/tip/README-builds.html
+See http://openjdk.java.net/ for more information about OpenJDK.