Include <stdlib.h> for abort, which libstdc++ pulls in elsewhere and libc++ does not.

--- a/test/hsa/copy.cpp
+++ b/test/hsa/copy.cpp
@@ -24,6 +24,7 @@
 
 #include <fcntl.h>
 #include <assert.h>
+#include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>