Add __attribute__ ((nonstring)) to remove unterminated-string-initialization warning

Signed-off-by: Felix Conway <felix.conway@arm.com>
diff --git a/tests/suites/test_suite_ssl_decrypt.function b/tests/suites/test_suite_ssl_decrypt.function
index 35f0adb..46f9617 100644
--- a/tests/suites/test_suite_ssl_decrypt.function
+++ b/tests/suites/test_suite_ssl_decrypt.function
@@ -37,7 +37,8 @@
     mbedtls_ssl_write_version(rec_good.ver,
                               MBEDTLS_SSL_TRANSPORT_STREAM,
                               version);
-    const char sample_plaintext[3] = "ABC";
+    /* We need to tell the compiler that we meant to leave out the null character. */
+    const char sample_plaintext[3] __attribute__ ((nonstring)) = "ABC";
     mbedtls_ssl_context ssl;
     mbedtls_ssl_init(&ssl);
     uint8_t *buf = NULL;