[gn build] Change python run lines to python3

[thakis]

Summary

macOS 12.3 no longer ships non-3 python.

Almost all of these scripts were launched by ninja, and the GN files
already told it to run them under python3, so this is a fairly small
change. The main effect is that if you run them manually, you now
get the same behavior.

(A small set of scripts, gn.py, gen.py, sync_source_lists_from_cmake.py,
are for manual running. For these, it is an actual change.)

llvm/utils/gn/build/run_tablegen.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Runs tablegen."""
 
 import subprocess
 import sys
 
 # Prefix with ./ to run built binary, not arbitrary stuff from PATH.
 sys.exit(subprocess.call(['./' + sys.argv[1]] + sys.argv[2:]))

llvm/utils/gn/build/symbol_exports.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 """Converts a .exports file to a format consumable by linkers.
 
 An .exports file is a file with one exported symbol per line.
 This script converts a .exports file into a format that linkers
 can understand:
 - It prepends a `_` to each line for use with -exported_symbols_list for Darwin
 - It writes a .def file for use with /DEF: for Windows

llvm/utils/gn/build/symlink_or_copy.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 """Symlinks, or on Windows copies, an existing file to a second location.
 
 Overwrites the target location if it exists.
 Updates the mtime on a stamp file when done."""
 
 import argparse
 import errno

llvm/utils/gn/build/sync_source_lists_from_cmake.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 """Helps to keep BUILD.gn files in sync with the corresponding CMakeLists.txt.
 
 For each BUILD.gn file in the tree, checks if the list of cpp files in
 it is identical to the list of cpp files in the corresponding CMakeLists.txt
 file, and prints the difference if not.
 
 Also checks that each CMakeLists.txt file below unittests/ folders that define
 binaries have corresponding BUILD.gn files.
 
 If --write is passed, tries to write modified .gn files and adds one git
 commit for each cmake commit this merges. If an error is reported, the state
 of HEAD is unspecified; run `git reset --hard origin/main` if this happens.
 """
 
-from __future__ import print_function
-
 from collections import defaultdict
 import os
 import re
 import subprocess
 import sys
 
 
 def patch_gn_file(gn_file, add, remove):

llvm/utils/gn/build/write_cmake_config.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 r"""Emulates the bits of CMake's configure_file() function needed in LLVM.
 
 The CMake build uses configure_file() for several things.  This emulates that
 function for the GN build.  In the GN build, this runs at build time instead
 of at generator time.
 
 Takes a list of KEY=VALUE pairs (where VALUE can be empty).
 
one of the following two lines:
 
         #define FOO [...]
         /* #undef FOO */
 
 Fails if any of the KEY=VALUE arguments aren't needed for processing the
 input file, or if the input file references keys that weren't passed in.
 """
 
-from __future__ import print_function
-
 import argparse
 import os
 import re
 import sys
 
 
 def main():
     parser = argparse.ArgumentParser(

llvm/utils/gn/build/write_library_dependencies.py

-#!/usr/bin/env python
-from __future__ import print_function
+#!/usr/bin/env python3
 
 import argparse
 import os
 import re
 import sys
 
 
 # FIXME: This should get outputs from gn.

llvm/utils/gn/build/write_vcsrevision.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 """Gets the current revision and writes it to VCSRevision.h."""
 
-from __future__ import print_function
-
 import argparse
 import os
 import subprocess
 import sys
 
 
 THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 LLVM_DIR = os.path.dirname(os.path.dirname(os.path.dirname(THIS_DIR)))

llvm/utils/gn/get.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Downloads a prebuilt gn binary to a place where gn.py can find it."""
 
 from __future__ import print_function
 
 import io
 import os
-try:
-    # In Python 3, we need the module urllib.reqest. In Python 2, this
-    # functionality was in the urllib2 module.
-    from urllib import request as urllib_request
-except ImportError:
-    import urllib2 as urllib_request
 import sys
+import urllib.request
 import zipfile
 
 
 def download_and_unpack(url, output_dir, gn):
     """Download an archive from url and extract gn from it into output_dir."""
     print('downloading %s ...' % url, end='')
     sys.stdout.flush()
-    data = urllib_request.urlopen(url).read()
+    data = urllib.request.urlopen(url).read()
     print(' done')
     zipfile.ZipFile(io.BytesIO(data)).extract(gn, path=output_dir)
 
 
 def set_executable_bit(path):
     mode = os.stat(path).st_mode
     mode |= (mode & 0o444) >> 2 # Copy R bits to X.
     os.chmod(path, mode) # No-op on Windows.

llvm/utils/gn/gn.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Calls `gn` with the right --dotfile= and --root= arguments for LLVM."""
 
 # GN normally expects a file called '.gn' at the root of the repository.
 # Since LLVM's GN build isn't supported, putting that file at the root
 # is deemed inappropriate, which requires passing --dotfile= and -root= to GN.
 # Since that gets old fast, this script automatically passes these arguments.
 
 import os

llvm/utils/gn/secondary/libcxx/utils/gen_link_script.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 #===----------------------------------------------------------------------===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 #===----------------------------------------------------------------------===##
 

llvm/utils/gn/secondary/llvm/include/llvm/Support/write_extension_def.py

-#!/usr/bin/env python
-from __future__ import print_function
+#!/usr/bin/env python3
 
 import argparse
 import os
 import sys
 
 
 def main():
     parser = argparse.ArgumentParser()

llvm/utils/gn/secondary/llvm/tools/llvm-config/write_extension_dependencies.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 r"""Writes ExtensionDepencencies.inc."""
 
-from __future__ import print_function
-
 import argparse
 import os
 import re
 import sys
 
 
 def main():
     parser = argparse.ArgumentParser(description=__doc__)