MBEDTLS_THREADING_PTHREAD and MBEDTLS_THREADING_C are required by
www/hiawatha.

Index: include/mbedtls/config.h
--- include/mbedtls/config.h.orig
+++ include/mbedtls/config.h
@@ -2129,7 +2129,7 @@
  *
  * Uncomment this to enable pthread mutexes.
  */
-//#define MBEDTLS_THREADING_PTHREAD
+#define MBEDTLS_THREADING_PTHREAD
 
 /**
  * \def MBEDTLS_USE_PSA_CRYPTO
@@ -3452,7 +3452,7 @@
  *
  * Enable this layer to allow use of mutexes within mbed TLS
  */
-//#define MBEDTLS_THREADING_C
+#define MBEDTLS_THREADING_C
 
 /**
  * \def MBEDTLS_TIMING_C