Add link to build instructions to README.md.

Author: Pavel Kovalenko

README.md

@@ -7,6 +7,8 @@ The original engine is used in S.T.A.L.K.E.R. Call of Pripyat game released by G
 It is a place to share ideas on what to implement, gather people that want to work on the engine,
 and work on the source code.
 
+Build instructions can be found [here](https://github.com/openxray/xray-16/blob/master/doc/howto/build.txt).
+
 If you find a bug or have an enhancement request, file an [Issue](https://github.com/openxray/xray-16/issues).
 
 Pull requests appreciated! Just check out