Add support for LC_NOTE and LC_BUILD_VERSION

[ronaldoussoren]

Original report by Laurent DORE (Bitbucket: ldore, GitHub: ldore).

---

iOs SDK 12 beta introduces the following two load commands in loader.h:

#define LC_NOTE 0x31 /* arbitrary data included within a Mach-O file */
#define LC_BUILD_VERSION 0x32 /* build for platform min OS version */

Where:

/*
 * LC_NOTE commands describe a region of arbitrary data included in a Mach-O
 * file.  Its initial use is to record extra data in MH_CORE files.
 */
struct note_command {
    uint32_t	cmd;		/* LC_NOTE */
    uint32_t	cmdsize;	/* sizeof(struct note_command) */
    char	data_owner[16];	/* owner name for this LC_NOTE */
    uint64_t	offset;		/* file offset of this data */
    uint64_t	size;		/* length of data region */
};

and:

/*
 * The build_version_command contains the min OS version on which this 
 * binary was built to run for its platform.  The list of known platforms and
 * tool values following it.
 */
struct build_version_command {
    uint32_t	cmd;		/* LC_BUILD_VERSION */
    uint32_t	cmdsize;	/* sizeof(struct build_version_command) plus */
                                /* ntools * sizeof(struct build_tool_version) */
    uint32_t	platform;	/* platform */
    uint32_t	minos;		/* X.Y.Z is encoded in nibbles xxxx.yy.zz */
    uint32_t	sdk;		/* X.Y.Z is encoded in nibbles xxxx.yy.zz */
    uint32_t	ntools;		/* number of tool entries following this */
};

struct build_tool_version {
    uint32_t	tool;		/* enum for the tool */
    uint32_t	version;	/* version number of the tool */
};

With :

/* Known values for the tool field above. */
#define TOOL_CLANG 1
#define TOOL_SWIFT 2
#define TOOL_LD	3

Supporting these load commands would be a step toward iOs 12 compatibility.

[ronaldoussoren]

Original comment by Ronald Oussoren (Bitbucket: ronaldoussoren, GitHub: ronaldoussoren).

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changeset ff4fc2e668c4 has initial support for this.

I'd like to teach the python version of build_version_command about the list of build_tool_version elements in the load command before I do a release, but will to a release later this week regardless.

BTW. What do you use macholib for?