Fix wrong ifdef in ssl_server2 & add test for it

This was found as a warning when running scripts/baremetal.sh --ram
--build-only manually, but it should have been found in a more automated way.
Adding -Werror so that future such issues will be caught by all.sh
(component_test_baremetal already invokes baremetal.sh --ram --build-only).

programs/ssl/ssl_server2.c

@@ -791,6 +791,7 @@ static int send_cb( void *ctx, unsigned char const *buf, size_t len )
     return( mbedtls_net_send( io_ctx->net, buf, len ) );
 }
 
+#if defined(SNI_OPTION) || !defined(MBEDTLS_SSL_CONF_AUTHMODE)
 /*
  * Return authmode from string, or -1 on error
  */
@@ -805,6 +806,7 @@ static int get_auth_mode( const char *s )
 
     return( -1 );
 }
+#endif /* SNI_OPTION || !MBEDTLS_SSL_CONF_AUTHMODE */
 
 /*
  * Used by sni_parse and psk_parse to handle coma-separated lists

scripts/baremetal.sh

@@ -214,6 +214,9 @@ baremetal_ram_build() {
     make clean
 
     CFLAGS="$BASE_CFLAGS $CFLAGS_CONFIG $CFLAGS_USER_CONFIG"
+    if [ "$build_only" -eq 1 ]; then
+        CFLAGS="$CFLAGS -Werror"
+    fi
 
     echo "Modifications: $BAREMETAL_USER_CONFIG"
     cat $BAREMETAL_USER_CONFIG | grep "^#define" | awk '{print "* " $0 }'
@@ -352,7 +355,7 @@ measure_heap=0
 measure_stack=0
 
 check=0
-
+build_only=0
 debug=0
 
 while [ $# -gt 0 ]; do