Bootstrap checkbuild.py with Python 3.

This allows us to implement checkbuild.py and its associated pieces
exclusively in Python 3 even though it isn't available on the build
servers. The version currently available in external/python/cpython3
is 3.6, so this gets us features even as new as type annotations and
f-strings.

On my P920 the bootstrapping step takes about a minute. When
bootstrapping is complete a .bootstrapped file is placed in the out
directory to avoid rebuilding Python every time.

We can't go through our existing Python 2 as an intermediate step
because we can't build the SSL (and therefore the hashlib) module for
that version of Python because it's not compatible with whatever is
on these machines (which might be BoringSSL?).

Test: ./checkbuild.py
Bug: None
Change-Id: Ie01a586cdbfaf22da3025aabbc3ed931480b7742

1 files changed, 28 insertions, 3 deletions

diff --git a/checkbuild.py b/checkbuild.py
index a718f6b9b..d85a719e4 100755
--- a/checkbuild.py
+++ b/checkbuild.py
@@ -19,20 +19,45 @@
 Differs from do_checkbuild.py because it launches a new Python interpreter,
 allowing this script to bootstrap our build with a specific version of Python.
 """
+import argparse
+import logging
+import os
 import subprocess
 import sys
 
+import ndk.bootstrap
 import ndk.paths
 
 
+def parse_args():
+    """Parses and returns command line arguments."""
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        '-v',
+        '--verbose',
+        action='count',
+        dest='verbosity',
+        help='Increase logging verbosity.')
+    return parser.parse_known_args()
+
+
 def main():
     """Program entry point.
 
     Bootstraps the real checkbuild wrapper, do_checkbuild.py.
     """
-    subprocess.check_call(
-        ['/usr/bin/env', 'python',
-         ndk.paths.ndk_path('do_checkbuild.py')] + sys.argv[1:])
+    args, _ = parse_args()
+
+    if args.verbosity >= 2:
+        logging.basicConfig(level=logging.DEBUG)
+    else:
+        logging.basicConfig(level=logging.INFO)
+
+    python_install = ndk.bootstrap.bootstrap()
+    subprocess.check_call([
+        os.path.join(python_install, 'bin/python3'),
+        ndk.paths.ndk_path('do_checkbuild.py')
+    ] + sys.argv[1:])
 
 
 if __name__ == '__main__':