For microblaze, replace the ONCE macro

For some reason the systemd developers decided that needed to hardcode
the usage of __sync_bool_compare_and_swap, however not all architectures
define this.  Microblaze is one such architecture, so we fall back to
a less 'safe' way of doing the work.  However a quick inspection of
the ONCE users shows that even if we end up with a race condition the
worst expected behavior could be multiple log messages.

Signed-off-by: Mark Hatle <mark.hatle@xilinx.com>

Index: git/src/fundamental/macro-fundamental.h
===================================================================
--- git.orig/src/fundamental/macro-fundamental.h
+++ git/src/fundamental/macro-fundamental.h
@@ -109,11 +109,28 @@
  * on this macro will run concurrently to all other code conditionalized
  * the same way, there's no ordering or completion enforced. */
 #define ONCE __ONCE(UNIQ_T(_once_, UNIQ))
+#if !defined (__microblaze__)
 #define __ONCE(o)                                                       \
         ({                                                              \
                 static sd_bool (o) = sd_false;                          \
                 __sync_bool_compare_and_swap(&(o), sd_false, sd_true);  \
         })
+#else
+  /* Microblaze does not contain __sync_bool_compare_and_swap, so we do it
+   * the old fashioned way.  Note, it's possible that ONCE may run more
+   * then ONCE due to possible races, however it is not expected to cause
+   * an issue. */
+#define __ONCE(o)                                                       \
+        ({                                                              \
+                static bool (o) = sd_false;                             \
+                bool rc = sd_false;                                     \
+                if ((o) == sd_false) {                                  \
+                        (o) = sd_true;                                  \
+                        rc = sd_true;                                   \
+                }                                                       \
+                rc;                                                     \
+        })
+#endif
 
 #undef MAX
 #define MAX(a, b) __MAX(UNIQ, (a), UNIQ, (b))