Add stat RPC

[JaewonHur]

This PR adds stat RPC to vminitd.

[dcantah]

Can we return a stat_t? And not the protobuf type directly?

[JaewonHur]

@dcantah updated to return Foundation.stat.

But, it doesn't compile when I set timespec fields there. It feels like because they are defined differently depending on the underlying OS.

#define __DARWIN_STRUCT_STAT64_TIMES \
	struct timespec st_atimespec;           /* time of last access */ \
	struct timespec st_mtimespec;           /* time of last data modification */ \
	struct timespec st_ctimespec;           /* time of last status change */ \
	struct timespec st_birthtimespec;       /* time of file creation(birth) */

#else /* (_POSIX_C_SOURCE && !_DARWIN_C_SOURCE) */

#define __DARWIN_STRUCT_STAT64_TIMES \
	time_t		st_atime;               /* [XSI] Time of last access */ \
	long		st_atimensec;           /* nsec of last access */ \
	time_t		st_mtime;               /* [XSI] Last data modification time */ \
	long		st_mtimensec;           /* last data modification nsec */ \
	time_t		st_ctime;               /* [XSI] Time of last status change */ \
	long		st_ctimensec;           /* nsec of last status change */ \
	time_t		st_birthtime;           /*  File creation time(birth)  */ \
	long		st_birthtimensec;       /* nsec of File creation time */

#endif /* (!_POSIX_C_SOURCE || _DARWIN_C_SOURCE) */

/*
 * This structure is used as the second parameter to the fstat64(),
 * lstat64(), and stat64() functions, and for struct stat when
 * __DARWIN_64_BIT_INO_T is set. __DARWIN_STRUCT_STAT64 is defined
 * above, depending on whether we use struct timespec or the direct
 * components.
 *
 * This is simillar to stat except for 64bit inode number
 * number instead of 32bit ino_t and the addition of create(birth) time.
 */
#define __DARWIN_STRUCT_STAT64 { \
	dev_t		st_dev;                 /* [XSI] ID of device containing file */ \
	mode_t		st_mode;                /* [XSI] Mode of file (see below) */ \
	nlink_t		st_nlink;               /* [XSI] Number of hard links */ \
	__darwin_ino64_t st_ino;                /* [XSI] File serial number */ \
	uid_t		st_uid;                 /* [XSI] User ID of the file */ \
	gid_t		st_gid;                 /* [XSI] Group ID of the file */ \
	dev_t		st_rdev;                /* [XSI] Device ID */ \
	__DARWIN_STRUCT_STAT64_TIMES \
	off_t		st_size;                /* [XSI] file size, in bytes */ \
	blkcnt_t	st_blocks;              /* [XSI] blocks allocated for file */ \
	blksize_t	st_blksize;             /* [XSI] optimal blocksize for I/O */ \
	__uint32_t	st_flags;               /* user defined flags for file */ \
	__uint32_t	st_gen;                 /* file generation number */ \
	__int32_t	st_lspare;              /* RESERVED: DO NOT USE! */ \
	__int64_t	st_qspare[2];           /* RESERVED: DO NOT USE! */ \
}

/*
 * [XSI] This structure is used as the second parameter to the fstat(),
 * lstat(), and stat() functions.
 */
#if __DARWIN_64_BIT_INO_T

struct stat __DARWIN_STRUCT_STAT64;

Do you have any workaround?