Add Mesa Vulkan drivers to CI image

ci/Dockerfile

@@ -44,6 +44,7 @@ RUN set -eux; \
       libvulkan-dev \
       vulkan-tools \
       vulkan-validationlayers \
+      mesa-vulkan-drivers \
       glslang-tools \
       spirv-tools \
       spirv-headers; \

ci/README.md

@@ -13,6 +13,7 @@ It includes:
 - Ninja
 - Python 3 + pip + venv
 - Vulkan development packages/tools
+- Mesa Vulkan software/runtime drivers
 - Git/build-essential/pkg-config
 - Node/runtime pieces inherited from the act Ubuntu image, so JavaScript actions like `actions/checkout` keep working
 

ci/USE_CI_IMAGE.md

@@ -30,6 +30,7 @@ It includes:
 - Ninja
 - Python 3 / pip / venv
 - Vulkan development packages/tools
+- Mesa Vulkan software/runtime drivers
 - `build-essential`
 - `pkg-config`
 - Git
@@ -491,7 +492,7 @@ Expected results:
 - `clang` should be version 22.
 - `meson` should print a version.
 - `ninja` should print a version.
-- `vulkaninfo --summary` may fail if the CI machine has no GPU/display/runtime Vulkan driver. That is usually okay for compile-only CI as long as Vulkan headers/tools are installed.
+- `vulkaninfo --summary` should usually find Mesa's software Vulkan driver. It may still fail on unusual container/runner setups; that is okay for compile-only CI as long as Vulkan headers/tools are installed.
 
 Exit: