runfvp: exit with the return code of the FVP binary

Change-Id: If79e31e61110161c9a13dd512b0146d1d515d77a
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

scripts/runfvp

@@ -154,7 +154,7 @@ def runfvp(args):
             logger.error(f"{fvp_process.args[0]} quit with code {fvp_process.returncode}:")
             logger.error(output)
     else:
-        subprocess.run(cli)
+        sys.exit(subprocess.run(cli).returncode)
 
 if __name__ == "__main__":
     runfvp(sys.argv)