Add output of build version in ssl_server2 and ssl_client2

Backport the changes in PR 6436 to mbedtls-2.28.

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 283216b..1f0ac55 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -466,6 +466,8 @@
     "    server_addr=%%s      default: (all interfaces)\n"  \
     "    server_port=%%d      default: 4433\n"              \
     "    debug_level=%%d      default: 0 (disabled)\n"      \
+    "    build_version=%%d    default: none (disabled)\n"                     \
+    "                        option: 1 (print build version only and stop)\n" \
     "    buffer_size=%%d      default: 200 \n" \
     "                         (minimum: 1, max: 16385)\n" \
     "    response_size=%%d    default: about 152 (basic response)\n" \
@@ -1588,6 +1590,16 @@
             if( opt.debug_level < 0 || opt.debug_level > 65535 )
                 goto usage;
         }
+        else if( strcmp( p, "build_version" ) == 0 )
+        {
+            if( strcmp( q, "1" ) == 0 )
+            {
+                mbedtls_printf( "build version: %s (build %d)\n",
+                                MBEDTLS_VERSION_STRING_FULL,
+                                MBEDTLS_VERSION_NUMBER );
+                goto exit;
+            }
+        }
         else if( strcmp( p, "nbio" ) == 0 )
         {
             opt.nbio = atoi( q );
@@ -2335,6 +2347,9 @@
     }
 #endif /* MBEDTLS_SSL_ALPN */
 
+    mbedtls_printf( "build version: %s (build %d)\n",
+                    MBEDTLS_VERSION_STRING_FULL, MBEDTLS_VERSION_NUMBER );
+
     /*
      * 0. Initialize the RNG and the session data
      */