[x264] enable cross-compile settings propagation for arm64-linux.

[sylvain-prevost]

• What does your PR fix?

  Fixes [x264] arm64 cross-compile settings are ignored. #22899

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

  ,

• 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?

[github-actions]

You have modified or added at least one vcpkg.json where a "license" field is missing.
If you feel able to do so, please consider adding a "license" field to the following files:

• ports/x264/vcpkg.json

Valid values for the license field are listed at https://spdx.org/licenses/

[BillyONeal]

This edit is substantially identical to #22331

[strega-nil-ms]

This edit is substantially identical to #22331

I'd say here that we should merge #22331, and then this change will be unneeded.

[sylvain-prevost]

Just reviewed #22331 and tested locally. Indeed It does solves the '--host' problem.
However the --cross-prefix problem still remains (this is expected by x264 ). I'll close this PR and wait for #22331 to be merged. Then I'll re-test and submit PR for x264 to cross-compile properly with user-specified toolchain.
(see line 557 of x264 configure-file: https://github.com/mirror/x264/blob/master/configure)