[Buildroot] [PATCH vRFC 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

- The clang toolchain wrapper does not work properly, resulting in the immediate
  errors of:
    -Wl,-z,now: 'linker' input unused
    -Wl,-z,relro: 'linker' input unused
  The solution is to use clang.br_real and clang++.br_real.

- If using per_package builds, flutter-engine tries to use the host /usr/bin/ld
  instead of the one provided by the compiler, resulting in linking errors.
  As such, if BR2_PER_PACKAGE_DIRECTORIES is enabled, we search for the ld
  provided by the compiler in the host directory and set the path accordingly.

- libtessellator.so (built by flutter) requires three files:
  crtbeginS.o crtendS.o libgcc.a. However, the toolchain path isn't referenced
  when linking. The solution is to copy those three files to the staging lib
  directory before building.

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 +
 .../0001-Disable-ninjalog-upload.patch        |  35 +++
 package/depot-tools/Config.in.host            |  10 +
 package/depot-tools/depot-tools.hash          |   3 +
 package/depot-tools/depot-tools.mk            |  33 ++
 .../0001-disable-pre-canned-sysroot.patch     |  32 ++
 .../0002-remove-explicit-x11-dependency.patch |  33 ++
 .../0003-disable-undefined-version.patch      |  32 ++
 ...onfig.py-do-not-prepend-sysroot-path.patch |  34 +++
 package/flutter-engine/Config.in              |  93 ++++++
 package/flutter-engine/flutter-engine.mk      | 286 ++++++++++++++++++
 package/flutter-engine/gclient                |  16 +
 package/python-httplib2/python-httplib2.mk    |   1 +
 15 files changed, 614 insertions(+)
 create mode 100644 package/depot-tools/0001-Disable-ninjalog-upload.patch
 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-disable-undefined-version.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/flutter-engine.mk
 create mode 100644 package/flutter-engine/gclient

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2.41.0