Declare GRUB_EFI_VENDOR_APPLE_GUID.

include/grub/efi/api.h

@@ -280,6 +280,12 @@
   { 0xb1b621d5, 0xf19c, 0x41a5, \
       { 0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0 } \
   }
+
+#define GRUB_EFI_VENDOR_APPLE_GUID \
+  { 0x2B0585EB, 0xD8B8, 0x49A9,	\
+      { 0x8B, 0x8C, 0xE2, 0x1B, 0x01, 0xAE, 0xF2, 0xB7 } \
+  }
+
 struct grub_efi_sal_system_table
 {
   grub_uint32_t signature;