[libass] switch the build system to meson and enable asm optimization

[Masaiki]

Describe the pull request

• What does your PR fix?

  switch the build system to meson and enable asm optimization, meson files from Port of the build system to meson libass/libass#330, with few changes.

• Which triplets are supported/not supported? Have you updated the CI baseline?

  all, Yes

• Does your PR follow the maintainer guide?

  Yes

• If you have added/updated a port: Have you run ./vcpkg x-add-version --all and committed the result?

  Yes

If you are still working on the PR, open it as a Draft: https://github.blog/2019-02-14-introducing-draft-pull-requests/

[Masaiki]

x64-windows and x86-windows failed because ass.lib was not generated.
I can't find out why...

[JackBoosY]

[20/21] "D:\downloads\tools\python\python-3.9.6-x64\python.exe" "D:\downloads\tools\meson\meson-aeda7f249c4a5dbbecc52e44f382246a2377b5b0\meson.py" "install" "--no-rebuild"
Installing libass\ass.dll to D:/packages/libass_x64-windows/debug\bin
Traceback (most recent call last):
  File "D:\downloads\tools\meson\meson-aeda7f249c4a5dbbecc52e44f382246a2377b5b0\mesonbuild\mesonmain.py", line 134, in run
    return options.run_func(options)
  File "D:\downloads\tools\meson\meson-aeda7f249c4a5dbbecc52e44f382246a2377b5b0\mesonbuild\minstall.py", line 719, in run
    installer.do_install(datafilename)
  File "D:\downloads\tools\meson\meson-aeda7f249c4a5dbbecc52e44f382246a2377b5b0\mesonbuild\minstall.py", line 511, in do_install
    self.install_targets(d, dm, destdir, fullprefix)
  File "D:\downloads\tools\meson\meson-aeda7f249c4a5dbbecc52e44f382246a2377b5b0\mesonbuild\minstall.py", line 614, in install_targets
    raise RuntimeError(f'File {t.fname!r} could not be found')
RuntimeError: File 'libass\\ass.lib' could not be found
FAILED: meson-install 
"D:\downloads\tools\python\python-3.9.6-x64\python.exe" "D:\downloads\tools\meson\meson-aeda7f249c4a5dbbecc52e44f382246a2377b5b0\meson.py" "install" "--no-rebuild"
ninja: build stopped: subcommand failed.

[Masaiki]

add patch from ShiftMediaProject/libass@9a92b60
add .def back to export functions.
request for a review @JackBoosY , thanks

[JackBoosY]

Depends on #19629.

[Masaiki]

Remove codes about subproject for vcpkg doesn't need it.

[JackBoosY]

Does the upstream not support meson now? I noticed you manually copied the meson scripts.

[Masaiki]

Does the upstream not support meson now? I noticed you manually copied the meson scripts.

meson scripts are from this pr libass/libass#330, and I do some fixes for it. upstream only support autoconf.

[JackBoosY]

@Masaiki Okay, let's wait for libass/libass#330 merge.

[JackBoosY]

Why close this?