Test POSIX 1003.1 2016 chapter 13 "Headers".

And fix one thing that this found: apparently <stdlib.h> should also
make the various *WAIT* macros available.

Bug: N/A
Test: builds
Change-Id: Id879bf3c1bddd1170261a809e7280150a74d6b3d
diff --git a/tests/Android.bp b/tests/Android.bp
index 28df084..7f69cb1 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -645,4 +645,4 @@
     },
 }
 
-subdirs = ["libs"]
+subdirs = ["*"]