guard against redefinition of irq functions

teensy core includes them already

include/cmsis_gcc.h

 #ifndef   __STATIC_INLINE
   #define __STATIC_INLINE                        static inline
 #endif
-#ifndef   __STATIC_FORCEINLINE                 
+#ifndef   __STATIC_FORCEINLINE
   #define __STATIC_FORCEINLINE                   __attribute__((always_inline)) static inline
-#endif                                           
+#endif
 #ifndef   __NO_RETURN
   #define __NO_RETURN                            __attribute__((__noreturn__))
 #endif
   \details This default implementations initialized all data and additional bss
            sections relying on .copy.table and .zero.table specified properly
            in the used linker script.
-  
+
  */
 __STATIC_FORCEINLINE __NO_RETURN void __cmsis_start(void)
 {
   extern void _start(void) __NO_RETURN;
-  
+
   typedef struct {
     uint32_t const* src;
     uint32_t* dest;
     uint32_t  wlen;
   } __copy_table_t;
-  
+
   typedef struct {
     uint32_t* dest;
     uint32_t  wlen;
   } __zero_table_t;
-  
+
   extern const __copy_table_t __copy_table_start__;
   extern const __copy_table_t __copy_table_end__;
   extern const __zero_table_t __zero_table_start__;
       pTable->dest[i] = pTable->src[i];
     }
   }
- 
+
   for (__zero_table_t const* pTable = &__zero_table_start__; pTable < &__zero_table_end__; ++pTable) {
     for(uint32_t i=0u; i<pTable->wlen; ++i) {
       pTable->dest[i] = 0u;
     }
   }
- 
+
   _start();
 }
-  
+
 #define __PROGRAM_START           __cmsis_start
 #endif
 
   @{
  */
 
+#ifndef TEENSYDUINO
+
 /**
   \brief   Enable IRQ Interrupts
   \details Enables IRQ interrupts by clearing the I-bit in the CPSR.
   __ASM volatile ("cpsid i" : : : "memory");
 }
 
+#endif /* TEENSYDUINO */
 
 /**
   \brief   Get Control Register
   Devices without ARMv8-M Main Extensions (i.e. Cortex-M23) lack the non-secure
   Stack Pointer Limit register hence zero is returned always in non-secure
   mode.
-  
+
   \details Returns the current value of the Process Stack Pointer Limit (PSPLIM).
   \return               PSPLIM Register value
  */
   Devices without ARMv8-M Main Extensions (i.e. Cortex-M23) lack the non-secure
   Stack Pointer Limit register hence the write is silently ignored in non-secure
   mode.
-  
+
   \details Assigns the given value to the Process Stack Pointer Limit (PSPLIM).
   \param [in]    ProcStackPtrLimit  Process Stack Pointer Limit value to set
  */
 {
 #if ((defined (__FPU_PRESENT) && (__FPU_PRESENT == 1U)) && \
      (defined (__FPU_USED   ) && (__FPU_USED    == 1U))     )
-#if __has_builtin(__builtin_arm_get_fpscr) 
+#if __has_builtin(__builtin_arm_get_fpscr)
 // Re-enable using built-in when GCC has been fixed
 // || (__GNUC__ > 7) || (__GNUC__ == 7 && __GNUC_MINOR__ >= 2)
   /* see https://gcc.gnu.org/ml/gcc-patches/2017-04/msg00443.html */