[fontconfig] Fix x86-osx -> arm64-osx cross-compilation

[Lucius-Q-User]

Pass host system cflags instead of target system cflags to tools that are supposed to run on host system.
Run host system version of fc-cache instead of target system.

• What does your PR fix?

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

  x86-osx, arm64-osx No

• 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/

[Neumann-A]

could you add:

if(NOT VCPKG_TARGET_IS_WINDOWS)
    list(APPEND OPTIONS "as_ln_s=ln -sr")
endif()

before vcpkg_configure_make

This also fixes the broken symlinks in fontconfig

[dg0yt]

Where does CFLAGS_FOR_BUILD come from, before #15605?

[PhoebeHui]

@Lucius-Q-User, I didn't find the CFLAGS_FOR_BUILD in fontconfig, so why do you change it?

[Lucius-Q-User]

CFLAGS refers to target system cflags, which can break the build, (e.g -arch flag for clang, or -march/-mcpu flags)

[dg0yt]

CFLAGS_FOR_BUILD might be set for cross builds after #15605, but for now you miss CFLAGS for native builds.
In addition, $(LIBINTL) can go wrong as well for cross builds.

[Lucius-Q-User]

Alternatively, we can update the version of fontconfig that is currently in the tree. Newer versions made fc-case, which is the source of cross-compile problems into a python script.

[Lucius-Q-User]

would it be ok to conditionally include cflags depending on whether we are cross-compiling or not?

[Lucius-Q-User]

could you add:

if(NOT VCPKG_TARGET_IS_WINDOWS)
    list(APPEND OPTIONS "as_ln_s=ln -sr")
endif()

before vcpkg_configure_make

This also fixes the broken symlinks in fontconfig

That breaks the build, macos version of ln does not support -r

[Lucius-Q-User]

Looks like simage was broken even before the patch.

[PhoebeHui]

simage failures would be fixed by PR #18645

[PhoebeHui]

@Lucius-Q-User, the dependency PR has been closed, does this PR still be valid? can I close it?

[Lucius-Q-User]

The dependency PR was closed because fontconfig was updated via a different PR. Since fontconfig was updated, it now uses a completely different build system (meson instead of automake) and this PR no longer applies.
The cross-compile is unfortunately still broken, but i believe that #21772 should be able to fix it.

[PhoebeHui]

@Lucius-Q-User, thanks for your response! It looks PR #21772 aim to solve the problem.

Closing in favor of #21772.