Fix NUCLEO_F767ZI build, add tests (#19746)

.github/workflows/test-builds.yml

         - STM32F103RET6_creality
         - LERDGEX
         - mks_robin_nano35
+        - NUCLEO_F767ZI
 
         # Put lengthy tests last
 

Marlin/src/pins/stm32f7/pins_NUCLEO_F767ZI.h

  */
 #pragma once
 
-#ifndef STM32F767xx
+#if NOT_TARGET(STM32F767xx)
   #error "Oops! Select an STM32F767 environment"
 #endif
 

buildroot/tests/NUCLEO_F767ZI-tests

+#!/usr/bin/env bash
+#
+# Build tests for NUCLEO_F767ZI
+#
+
+# exit on first failure
+set -e
+
+#
+# Build with the default configurations
+#
+restore_configs
+opt_set MOTHERBOARD BOARD_NUCLEO_F767ZI
+opt_set SERIAL_PORT -1
+opt_enable BLTOUCH Z_SAFE_HOMING SPEAKER
+opt_set X_DRIVER_TYPE TMC2209
+opt_set Y_DRIVER_TYPE TMC2208
+exec_test $1 $2 "Mixed timer usage"
+
+# clean up
+restore_configs