Stop using ../../test_common to include common headers

Fixes #395.

Signed-off-by: Kevin Petit <kevin.petit@arm.com>

test_conformance/basic/test_async_copy.cpp

@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-#include "../../test_common/harness/compat.h"
+#include "harness/compat.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -24,7 +24,7 @@
 
 
 #include "procs.h"
-#include "../../test_common/harness/conversions.h"
+#include "harness/conversions.h"
 
 static const char *async_global_to_local_kernel =
 "%s\n" // optional pragma string