Make vboot_reference build in MSVC command line environment.

firmware/lib/include/vboot_struct.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.
  *
  * Data structure definitions for verified boot, for on-disk / in-eeprom
  * data.
  */
 
 #ifndef VBOOT_REFERENCE_VBOOT_STRUCT_H_
 #define VBOOT_REFERENCE_VBOOT_STRUCT_H_
 
 #include "sysincludes.h"
 
-#ifdef _MSC_VER
-#pragma pack(push, 1) /* Support packing for MSVC. */
-#endif
+__pragma(pack(push, 1)) /* Support packing for MSVC. */
 
 /* Public key data */
 typedef struct VbPublicKey {
   uint64_t key_offset;     /* Offset of key data from start of this struct */
   uint64_t key_size;       /* Size of key data in bytes (NOT strength of key
                            * in bits) */
   uint64_t algorithm;      /* Signature algorithm used by the key */
   uint64_t key_version;    /* Key version */
 } __attribute__((packed)) VbPublicKey;
 
@@ skipping 99 matching lines @@
   VbSignature body_signature;        /* Signature for the kernel body */
 } __attribute__((packed)) VbKernelPreambleHeader;
 /* This should be followed by:
  *   2) The signature data for the kernel body, pointed to by
  *      body_signature.sig_offset.
  *   3) The signature data for (VBFirmwarePreambleHeader + body signature
  *      data), pointed to by preamble_signature.sig_offset. */
 
 #define EXPECTED_VBKERNELPREAMBLEHEADER_SIZE 96
 
-#ifdef _MSC_VER
-#pragma pack(pop) /* Support packing for MSVC. */
-#endif
+__pragma(pack(pop)) /* Support packing for MSVC. */
 
 #endif  /* VBOOT_REFERENCE_VBOOT_STRUCT_H_ */