[Buildroot] [PATCH/next vRFCv2 0/3] Initial flutter packages

[Adam Duskett]

Preface: Thank you for all the help, thoughts and insight for this initial
RFC of the flutter-engine library. There are many other flutter packages that
need to be ported, but this is the largest hurdle to overcome.

There are many issues with the flutter-engine package:

- The release tarballs from https://github.com/flutter/engine are in no state
  to compile. They are only for the use of gclient to download a source
  directory structure suitable to build the Flutter engine! If you download,
  extract and attempt to run `./tools/gn --no-goma --no-prebuilt-dart-sdk`, you
  receive the error message:
  `No such file or directory: 'flutter/flutter/third_party/gn/gn.'

  But wait! Wasn't the gn binary just called? No, that's a wrapper in the
  Flutter source tree that formats arguments to call the real gn binary.
  The real gn is not provided in the tarball but is downloaded via gclient
  (among many other supporting repositories.)

  Even worse, the flutter repository depends on the .git dirs being present.
  (https://github.com/meta-flutter/meta-flutter/issues/271) This dependency
  means it is not possible to create a reproducible tarball from the downloaded
  sources, which is why there is no .hash file provided.

  I have asked the flutter project to release full tarballs suitable for
  compiling here: https://github.com/flutter/flutter/issues/130734

- Flutter engine includes a patched copy of clang that must be used to compile.
  Using a Buildroot-build clang results in linking warning and errors.
  As such, we depend on LLVM_ARCH_SUPPORTS but use the included clang for
  building. On the plus side, this saves time having to compile clang.

Tested with:
  - Debian 11 and 12
  - Ubuntu 18.04, 20.04, and 22.04
  - Fedora 38
  - Per package directory enabled and disabled
  - x86_64, arm64

Adam Duskett (3):
  package/python-httplib2: add host variant
  package/depot-tools: new package
  package/flutter-engine: new package

 DEVELOPERS                                    |   4 +
 package/Config.in                             |   1 +
 package/Config.in.host                        |   1 +
 package/depot-tools/Config.in.host            |  10 +
 package/depot-tools/depot-tools.hash          |   3 +
 package/depot-tools/depot-tools.mk            |  30 +++
 .../0001-disable-pre-canned-sysroot.patch     |  32 +++
 .../0002-remove-explicit-x11-dependency.patch |  33 +++
 .../0003-fix-toolchain-paths.patch            |  40 +++
 ...onfig.py-do-not-prepend-sysroot-path.patch |  34 +++
 package/flutter-engine/Config.in              |  60 +++++
 package/flutter-engine/dot-gclient            |  16 ++
 package/flutter-engine/flutter-engine.mk      | 239 ++++++++++++++++++
 package/flutter-engine/gen-tarball            | 108 ++++++++
 package/python-httplib2/python-httplib2.mk    |   1 +
 15 files changed, 612 insertions(+)
 create mode 100644 package/depot-tools/Config.in.host
 create mode 100644 package/depot-tools/depot-tools.hash
 create mode 100644 package/depot-tools/depot-tools.mk
 create mode 100644 package/flutter-engine/0001-disable-pre-canned-sysroot.patch
 create mode 100644 package/flutter-engine/0002-remove-explicit-x11-dependency.patch
 create mode 100644 package/flutter-engine/0003-fix-toolchain-paths.patch
 create mode 100644 package/flutter-engine/0004-pkg-config.py-do-not-prepend-sysroot-path.patch
 create mode 100644 package/flutter-engine/Config.in
 create mode 100644 package/flutter-engine/dot-gclient
 create mode 100644 package/flutter-engine/flutter-engine.mk
 create mode 100755 package/flutter-engine/gen-tarball

-- 
Changes v1 -> v2:
  - Remove unecessary patch (We aren't using ninjalog)
  - Formatting cleanup [Yann]
  - Remove uncessary environment variables for gclient [Yann]
  - Use the flutter-engine provided clang.
  - Remove 0003-disable-undefined-version.patch
  - Add 0003-fix-toolchain-paths.patch
  - Fix signed-off-by lines in the patches [Yann]
  - Remove "Runtime mode" option in favor of checking BR2_ENABLE_RUNTIME_DEBUG [Yann]
  - Use positive logic in flutter-engine.mk [Yann]
  - Add comments when --disable-${option} doesn't exist. [Yann]
  - Remove unecessary subshells in flutter-engine.mk [Yann]
  - Rename flutter-engine/gclient to flutter-engine/dot-gclient [Yann]
  - Create flutter-engine/gen-tarball to generate the flutter-engine tarball. [Yann]
  - Remove finding and copying crtbeginS.o crtendS.o libgcc.a as it's
    unecessary when using the flutter-engine provided clang.
  - FLUTTER_ENGINE_INSTALL_STAGING_FILES -> FLUTTER_ENGINE_INSTALL_FILES [Yann]
  - Reword comments at the top of flutter-engine.mk for clarity.
2.41.0