Fix missing RuntimeError header dependency

src/libsac/hwloc/cpubind.h

 #ifndef _SAC_HWLOC_LIB_H_
 #define _SAC_HWLOC_LIB_H_
 
+#if ENABLE_HWLOC
+
 #include <stddef.h>
 #include <hwloc.h>
 
@@ -22,4 +24,5 @@ extern hwloc_cpuset_t *SAC_HWLOC_get_core (hwloc_cpuset_t);
 extern void SAC_HWLOC_init (void);
 extern void SAC_HWLOC_cleanup (void);
 
+#endif /* ENABLE_HWLOC */
 #endif /* _SAC_HWLOC_LIB_H_ */

src/libsac/hwloc/cudabind.c

@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 
+#include "libsac/essentials/message.h"
 #include "cudabind.h"
 
 #if ENABLE_CUDA && ENABLE_HWLOC
@@ -14,7 +15,6 @@
 #include <hwloc/cudart.h>
 
 #include "libsac/hwloc/cpubind.h"
-#include "libsac/essentials/message.h"
 
 /**
  * Function initialises the HWLOC sub-system for use with CUDA-backend.