cmake docs add note about prefix

Signed-off-by: Andy Green <andy.green@linaro.org>

diff --git a/README.build b/README.build
index 68f4b4a..2787bde 100644 (file)
--- a/README.build
+++ b/README.build
@@ -292,6 +292,12 @@ Building on Unix:
         the source directory of libwebsockets containing the CMakeLists.txt project
         file. All examples in this file assumes you use "..")
 
+       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
+
 4. Finally you can build using the generated Makefile:
 
        make