cmake lib lib64 problem

As discussed here, there's a semi-standardized way to inform
cmake that the install target wants its libs in .../lib64

https://code.google.com/p/bullet/issues/detail?id=174

this patch adds the necessary fiddling

Signed-off-by: Andy Green <andy.green@linaro.org>
diff --git a/README.build b/README.build
index 64d98cf..3994c9c 100644
--- a/README.build
+++ b/README.build
@@ -283,12 +283,19 @@
 	 the source directory of libwebsockets containing the CMakeLists.txt project
 	 file. All examples in this file assumes you use "..")
 
+	NOTE2
 	A common option you may want to give is to set the install path, same
 	as --prefix= with autotools.  It defaults to /usr/local.
 	You can do this by, eg
 
 	cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr
 
+	NOTE3
+	On machines that want libraries in lib64, you can also add the
+	following to the cmake line
+
+		-DLIB_SUFFIX=64
+
 4. Finally you can build using the generated Makefile:
 
 	make