RISC-V-Qemu-virt: Add assert macros in FreeRTOSConfig (FreeRTOS#777)

vAssertCalled() is already defined in main.c. We need to set the
related macros in FreeRTOSConfig header as well, or the boundary
checking through assert could not be executed

FreeRTOS/Demo/RISC-V-Qemu-virt_GCC/FreeRTOSConfig.h

@@ -20,7 +20,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  *
  * https://www.FreeRTOS.org
- * https://www.github.com/FreeRTOS
+ * https://github.com/FreeRTOS
  *
  */
 
@@ -67,6 +67,11 @@
 #define configGENERATE_RUN_TIME_STATS	0
 #define configUSE_PORT_OPTIMISED_TASK_SELECTION 1
 
+/* Assert definitions. */
+void vAssertCalled( void );
+#define configASSERT_DEFINED                   1
+#define configASSERT( x )                      do { if ( !(x) ) vAssertCalled(); } while(0)
+
 /* Co-routine definitions. */
 #define configUSE_CO_ROUTINES 			0
 #define configMAX_CO_ROUTINE_PRIORITIES ( 2 )