Update meson command in README.md

The README.md file contains a recommended meson command for building
this repository.

The meson 'setup' action is implied if no action is specified.  In newer
versions of meson this behavior has been deprecated.  Explicitly specify
the 'setup' action in README.md.

Change-Id: Icce6352c74b42edeeeb68c5077764f6bfc228ea8
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
diff --git a/README.md b/README.md
index 314679d..8df14f5 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@
 To build all applications in this repository:
 
 ```
-  meson build
+  meson setup build
   ninja -C build
 ```