Make vboot_reference build in MSVC command line environment.

firmware/lib/cgptlib/include/gpt.h

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Defines EFI related structure. See more details in EFI 2.3 spec.
  *
  * To download EFI standard, please visit UEFI homepage:
  *    http://www.uefi.org/
  */
 #ifndef VBOOT_REFERENCE_CGPTLIB_GPT_H_
 #define VBOOT_REFERENCE_CGPTLIB_GPT_H_
 
 #include "sysincludes.h"
 
-#ifdef _MSC_VER
-#pragma pack(push,1) /* Support packing for MSVC. */
-#endif
+__pragma(pack(push,1)) /* Support packing for MSVC. */
 
 #define GPT_HEADER_SIGNATURE "EFI PART"
 #define GPT_HEADER_SIGNATURE_SIZE sizeof(GPT_HEADER_SIGNATURE)
 #define GPT_HEADER_REVISION 0x00010000
 
 /* The first 3 numbers should be stored in network-endian format
  * according to the GUID RFC.  The UEFI spec appendix A claims they
  * should be stored in little-endian format.  But they need to be
  * _displayed_ in network-endian format, which is also how they're
  * documented in the specs.
@@ skipping 82 matching lines @@
       uint16_t gpt_att;
     } __attribute__((packed)) fields;
     uint64_t whole;
   } attrs;
   uint16_t name[36];                    /* UTF-16 encoded partition name */
   /* Remainder of entry is reserved and should be 0 */
 } __attribute__((packed)) GptEntry;
 
 #define GPTENTRY_EXPECTED_SIZE 128
 
-#ifdef _MSC_VER
-#pragma pack(pop) /* Support packing for MSVC. */
-#endif
+__pragma(pack(pop)) /* Support packing for MSVC. */
 
 #endif  /* VBOOT_REFERENCE_CGPTLIB_GPT_H_ */