chromiumDev: Add the missing clang-format binary

The fix from 1d961a4c6d was unfortunately incomplete. This commit fixes
the second error [0] that occurs later during the build (the Python
script third_party/blink/renderer/bindings/scripts/generate_bindings.py
requires buildtools/linux64/clang-format).

[0]: https://github.com/NixOS/nixpkgs/pull/81016#issuecomment-591572821

pkgs/applications/networking/browsers/chromium/common.nix

@@ -7,7 +7,7 @@
 , xdg_utils, yasm, minizip, libwebp
 , libusb1, pciutils, nss, re2, zlib
 
-, python2Packages, perl, pkgconfig
+, python2Packages, perl, pkgconfig, clang-tools
 , nspr, systemd, kerberos
 , utillinux, alsaLib
 , bison, gperf
@@ -104,6 +104,8 @@ let
             result
        else result;
 
+  llvm-clang-tools = clang-tools.override { inherit llvmPackages; };
+
   base = rec {
     name = "${packageName}-unwrapped-${version}";
     inherit (upstream-info) channel version;
@@ -214,6 +216,8 @@ let
       ln -s ${stdenv.cc}/bin/clang              third_party/llvm-build/Release+Asserts/bin/clang
       ln -s ${stdenv.cc}/bin/clang++            third_party/llvm-build/Release+Asserts/bin/clang++
       ln -s ${llvmPackages.llvm}/bin/llvm-ar    third_party/llvm-build/Release+Asserts/bin/llvm-ar
+    '' + optionalString (stdenv.lib.versionAtLeast version "82") ''
+      ln -s ${llvm-clang-tools}/bin/clang-format buildtools/linux64/clang-format
     '';
 
     gnFlags = mkGnFlags ({