fix(linux): guard wlroots Vulkan calls in builds without Vulkan

Description

Building Wayland capture with SUNSHINE_ENABLE_VULKAN=OFF fails to link because wlr_vram_t still references vk::make_avcodec_encode_device_vram and vk::get_supported_capture_modifiers. Guard both references with SUNSHINE_BUILD_VULKAN, matching the adjacent CUDA and VA-API guards. The Vulkan-enabled code remains unchanged.

Screenshot

Issues Fixed or Closed

Found while building a local fix for the TLS shutdown hang tracked in #5617; this build fix is independent.

Roadmap Issues

Testing

• Reproduced both unresolved Vulkan symbol errors with Wayland enabled and Vulkan disabled.
• After the guards, configured and linked both sunshine and test_sunshine natively on Linux aarch64 with -DSUNSHINE_ENABLE_WAYLAND=ON -DSUNSHINE_ENABLE_VULKAN=OFF.
• Started the resulting binary on Hyprland and verified Wayland monitor discovery, H.264 encoder discovery, HTTPS responses, and the authenticated web UI.
• 88 focused HTTPS, pairing, authorization, network, codec-advertisement, and RTSP tests passed.
• Ran the project clang-format command and git diff --check.
• This is a disabled-feature compile/link regression; validation uses the affected native build configuration rather than a runtime unit test for unavailable Vulkan functionality. A Vulkan-enabled build was not run.

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Tests have been added or updated for new or modified functionality, including regression tests for bug fixes

AI Usage

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• AI tools were used while preparing this PR

Prepared by Codex (GPT-6; reasoning effort is not exposed by this session).