Roll buildroot to pick up iOS 12

[jmagman]

flutter/buildroot#804
flutter/buildroot#806
flutter/buildroot#808
flutter/buildroot#809
flutter/buildroot#810

Engine tests were already running on iOS 13.

Part of flutter/flutter#140474

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[zanderso]

@jason-simmons this PR has the failure that needs the fix to the sed command I mentioned here flutter/buildroot#806 (review)

[jmagman]

@jason-simmons this roll has sed issues:

Generating GN files in: out/wasm_release
ERROR at //build/toolchain/gcc_toolchain.gni:128:27: Assignment had no effect.
      sed_in_place_flag = "-i"

https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8759705668090838113/+/u/gn_--web_--runtime-mode_release_--no-goma_--no-lto/stdout

[zanderso]

@jmagman I edited this PR to pick up another patch from @jason-simmons and rebased.

[zanderso]

Ohh, the change to the sed flag is somehow leaking into the clang-tidy command?

error: unknown argument: '-i' [clang-diagnostic-error]

[jason-simmons]

Yes - confirmed locally that the compile_commands.json file used by the clang-tidy script will now contain the sed command if it was generated with Goma enabled by default.

Working on a patch that will filter out the sed command when clang-tidy builds Command.tidyArgs.

[jmagman]

Why aren't these showing up during clang-tidy and not compilation? Filed flutter/flutter#141130

Found compiler error(s).
error: unknown argument: '-i' [clang-diagnostic-error]

Yes - confirmed locally that the compile_commands.json file used by the clang-tidy script will now contain the sed command if it was generated with Goma enabled by default.

Working on a patch that will filter out the sed command when clang-tidy builds Command.tidyArgs.

Is the problem that compile_commands.json contains the sed command, or is it that the -i argument is still unknown?

[jason-simmons]

This is happening because the engine's clang-tidy wrapper script is parsing compile_commands.json to find the build's compile commands and convert them into clang-tidy commands.

The clang-tidy wrapper is not expecting the sed part of the compile command and is generating an invalid clang-tidy command.