[gn build] (manually) merge 24ab9b53 more

write_vcsrevision("write_vcsrevision") {

  header = "$target_gen_dir/VCSRevision.h"

}

# Corresponds to process_llvm_pass_plugins() in the CMake build.

# For now, just turn everything off.

# If we ever add real support for this, the GN way for this is probably

# to have a declare_args() list with plugin names that people can override

# in their args.gn and with empty defaults (similar to llvm_targets_to_build).

action("write_extension_def") {

  script = "//llvm/utils/gn/secondary/llvm/include/llvm/Support/write_extension_def.py"

  outputs = [

    "$target_gen_dir/Extension.def",

  ]

  # If any extensions should be enabled, they'd be passed as additional

  # arguments, e.g. `args += [ "Bye", "Polly" ]`.

  args = [

    "-o",

    rebase_path(outputs[0], root_build_dir),

  ]

}

#!/usr/bin/env python

from __future__ import print_function

import argparse

import os

import sys

def main():

    parser = argparse.ArgumentParser()

    parser.add_argument('exts', nargs='*', help='list of supported extensions')

    parser.add_argument('-o', '--output', required=True, help='output file')

    args = parser.parse_args()

    output = ''.join(['HANDLE_EXTENSION(%s)\n' % ext for ext in args.exts])

    if not os.path.exists(args.output) or open(args.output).read() != output:

        open(args.output, 'w').write(output)

if __name__ == '__main__':

    sys.exit(main())

    # public_dep because public header TargetSelect.h includes these .def files.

    "//llvm/include/llvm/Config:write_target_def_files",

    # public_dep because random targets assume its output exists.

    "//llvm/include/llvm/Support:write_extension_def",

  ]

  include_dirs = [

    "Unix",