FreeRTOS_Plus_TCP_Echo_Qemu_mps2: fix compile with "gcc -flto" (FreeRTOS#1343)

FreeRTOS_Plus_TCP_Echo_Qemu_mps2: fix compile with "gcc -flto"
by adding "__attribute__( used )" to isr_vector and _fstat().

Signed-off-by: Florian La Roche <[email protected]>

Author: laroche

FreeRTOS-Plus/Demo/FreeRTOS_Plus_TCP_Echo_Qemu_mps2/startup.c

@@ -167,7 +167,7 @@ static void Default_Handler6( void )
     }
 }
 
-const uint32_t * const isr_vector[] __attribute__( ( section( ".isr_vector" ) ) ) =
+const uint32_t * const isr_vector[] __attribute__( ( section( ".isr_vector" ), used ) ) =
 {
     ( uint32_t * ) &_estack,
     ( uint32_t * ) &Reset_Handler,       /* Reset                -15  */

FreeRTOS-Plus/Demo/FreeRTOS_Plus_TCP_Echo_Qemu_mps2/syscalls.c

@@ -30,7 +30,7 @@ extern "C" {
 #include <sys/types.h>
 
 void uart_init( void );
-int _fstat( int file );
+__attribute__( ( used ) ) int _fstat( int file );
 int _read( int file,
            char * buf,
            int len );