uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

pkgs/applications/virtualization/crosvm/update.py

@@ -0,0 +1,92 @@
+#! /usr/bin/env nix-shell
+#! nix-shell -p nix-prefetch-git "python3.withPackages (ps: with ps; [ lxml ])"
+#! nix-shell -i python
+
+import base64
+import json
+import re
+import shlex
+import subprocess
+from codecs import iterdecode
+from os.path import abspath, dirname, splitext
+from lxml import etree
+from lxml.etree import HTMLParser
+from urllib.request import urlopen
+
+git_path = 'chromiumos/platform/crosvm'
+git_root = 'https://chromium.googlesource.com/'
+manifest_versions = f'{git_root}chromiumos/manifest-versions'
+buildspecs_url = f'{manifest_versions}/+/refs/heads/master/full/buildspecs/'
+
+# CrOS version numbers look like this:
+# [<chrome-major-version>.]<tip-build>.<branch-build>.<branch-branch-build>
+#
+# As far as I can tell, branches are where internal Google
+# modifications are added to turn Chromium OS into Chrome OS, and
+# branch branches are used for fixes for specific devices.  So for
+# Chromium OS they will always be 0.  This is a best guess, and is not
+# documented.
+with urlopen('https://cros-updates-serving.appspot.com/') as resp:
+    document = etree.parse(resp, HTMLParser())
+    # bgcolor="lightgreen" is set on the most up-to-date version for
+    # each channel, so find a lightgreen cell in the "Stable" column.
+    (platform_version, chrome_version) = document.xpath("""
+        (//table[@id="cros-updates"]/tr/td[1 + count(
+            //table[@id="cros-updates"]/thead/tr[1]/th[text() = "Stable"]
+            /preceding-sibling::*)
+        ][@bgcolor="lightgreen"])[1]/text()
+    """)
+
+chrome_major_version = re.match(r'\d+', chrome_version)[0]
+chromeos_tip_build = re.match(r'\d+', platform_version)[0]
+
+# Find the most recent buildspec for the stable Chrome version and
+# Chromium OS build number.  Its branch build and branch branch build
+# numbers will (almost?) certainly be 0.  It will then end with an rc
+# number -- presumably these are release candidates, one of which
+# becomes the final release.  Presumably the one with the highest rc
+# number.
+with urlopen(f'{buildspecs_url}{chrome_major_version}/?format=TEXT') as resp:
+    listing = base64.decodebytes(resp.read()).decode('utf-8')
+    buildspecs = [(line.split('\t', 1)[1]) for line in listing.splitlines()]
+    buildspecs = [s for s in buildspecs if s.startswith(chromeos_tip_build)]
+    buildspecs.sort(reverse=True)
+    buildspec = splitext(buildspecs[0])[0]
+
+# Read the buildspec, and extract the git revision.
+with urlopen(f'{buildspecs_url}{chrome_major_version}/{buildspec}.xml?format=TEXT') as resp:
+    xml = base64.decodebytes(resp.read())
+    root = etree.fromstring(xml)
+    revision = root.find(f'./project[@name="{git_path}"]').get('revision')
+
+# Initialize the data that will be output from this script.  Leave the
+# rc number in buildspec so nobody else is subject to the same level
+# of confusion I have been.
+data = {'version': f'{chrome_major_version}.{buildspec}'}
+
+# Fill in the 'src' key with the output from nix-prefetch-git, which
+# can be passed straight to fetchGit when imported by Nix.
+argv = ['nix-prefetch-git',
+        '--fetch-submodules',
+        '--url', git_root + git_path,
+        '--rev', revision]
+output = subprocess.check_output(argv)
+data['src'] = json.loads(output.decode('utf-8'))
+
+# Find the path to crosvm's default.nix, so the src data can be
+# written into the same directory.
+argv = ['nix-instantiate', '--eval', '--json', '-A', 'crosvm.meta.position']
+position = json.loads(subprocess.check_output(argv).decode('utf-8'))
+filename = re.match(r'[^:]*', position)[0]
+
+# Write the output.
+with open(dirname(filename) + '/upstream-info.json', 'w') as out:
+    json.dump(data, out, indent=2)
+    out.write('\n')
+
+# Generate a Cargo.lock
+run = ['.',
+       dirname(abspath(__file__)) + '/generate-cargo.sh',
+       dirname(filename) + '/Cargo.lock']
+expr = '(import ./. {}).crosvm.overrideAttrs (_: { dontCargoSetupPostUnpack = true; })'
+subprocess.run(['nix-shell', '-E', expr, '--run', shlex.join(run)])