Make libc-builtin buffered printf be a common feature (#1483)

Add macros to control whether to use the libc-builtin buffered printf
and the buffer size.

core/shared/platform/nuttx/platform_internal.h

@@ -77,6 +77,10 @@ typedef sem_t korp_sem;
 #define CONFIG_HAS_ISATTY 0
 #endif
 
+#define BUILTIN_LIBC_BUFFERED_PRINTF 1
+#define BUILTIN_LIBC_BUFFERED_PRINT_SIZE 128
+#define BUILTIN_LIBC_BUFFERED_PRINT_PREFIX
+
 /*
  * NuttX doesn't have openat family.
  */