l8w8jwt: fix build with gcc15 (#508112)

diff --git a/lib/mbedtls/library/ssl_tls13_keys.c b/lib/mbedtls/library/ssl_tls13_keys.c

index dbc703a6c124961cfe38973ed4a0cae4867ba870..51afb044ccf3892bd0d69ec06b1f0ab0d15c287d 100644

--- a/lib/mbedtls/library/ssl_tls13_keys.c

+++ b/lib/mbedtls/library/ssl_tls13_keys.c

@@ -80,7 +80,8 @@ struct mbedtls_ssl_tls13_labels_struct const mbedtls_ssl_tls13_labels =

  *            the HkdfLabel structure on success.

  */

-static const char tls13_label_prefix[6] = "tls13 ";

+/* We need to tell the compiler that we meant to leave out the null character. */

+static const char tls13_label_prefix[6] __attribute__ ((nonstring)) = "tls13 ";

 #define SSL_TLS1_3_KEY_SCHEDULE_HKDF_LABEL_LEN(label_len, context_len) \

     (2                     /* expansion length           */ \

diff --git a/lib/mbedtls/library/ssl_tls13_keys.h b/lib/mbedtls/library/ssl_tls13_keys.h

index 14f6e4876c64b7562eef7de589f92c1fd84b190a..f6d02b522a5e3f4a6f6802ae7655dee07218f8d1 100644

--- a/lib/mbedtls/library/ssl_tls13_keys.h

+++ b/lib/mbedtls/library/ssl_tls13_keys.h

@@ -40,8 +40,9 @@

 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)

+/* We need to tell the compiler that we meant to leave out the null character. */

 #define MBEDTLS_SSL_TLS1_3_LABEL(name, string)       \

-    const unsigned char name    [sizeof(string) - 1];

+    const unsigned char name    [sizeof(string) - 1] __attribute__ ((nonstring));

 union mbedtls_ssl_tls13_labels_union {

     MBEDTLS_SSL_TLS1_3_LABEL_LIST

    hash = "sha256-aR3r84AYvCNx3jm9lB1qtbbEh9rU3LTkI+TK9LPQaPk=";

  };

  patches = [

    # adapted from https://github.com/Mbed-TLS/mbedtls/commit/79b513894a28718604f7cb531380bfea0354844f

    ./fix-gcc15.patch

  ];

  nativeBuildInputs = [ cmake ];

  cmakeFlags = [