Fix valgrind docs to build with mmma.

Rather than assume that all the prerequisites have already been built.

Change-Id: Id309752e34724d21d140a55db199607b105e92c3
diff --git a/src/devices/tech/debug/index.jd b/src/devices/tech/debug/index.jd
index 648c998..d45fafd 100644
--- a/src/devices/tech/debug/index.jd
+++ b/src/devices/tech/debug/index.jd
@@ -159,7 +159,7 @@
 <ol>
   <li>To install Valgrind, run:
 <pre>
-$ mmm -j6 external/valgrind
+$ mmma -j6 external/valgrind
 </pre>
   <li>Push Valgrind to the device:
     <br>