Disable sched_policy under Windows.

This introduces a new HAVE_SCHED_H arch define, which is used
to prevent from building sched_policy.c during the Windows SDK.

Change-Id: I3667857a4ae7d6baaf1efd1cd187a5baf91419d8
diff --git a/libcutils/sched_policy.c b/libcutils/sched_policy.c
index 8c7d611..7553090 100644
--- a/libcutils/sched_policy.c
+++ b/libcutils/sched_policy.c
@@ -1,3 +1,4 @@
+
 /* libs/cutils/sched_policy.c
 **
 ** Copyright 2007, The Android Open Source Project
@@ -21,6 +22,9 @@
 #include <string.h>
 #include <errno.h>
 #include <fcntl.h>
+
+#ifdef HAVE_SCHED_H
+
 #include <sched.h>
 
 #include <cutils/sched_policy.h>
@@ -89,3 +93,5 @@
 
     return 0;
 }
+
+#endif /* HAVE_SCHED_H */