Fix Vulkan icd selection

#105 burmalda ili govnolda

include/runtime/graphics_launch_policy.h

@@ -1,13 +1,23 @@
 #ifndef MOCKTAIL_RUNTIME_GRAPHICS_LAUNCH_POLICY_H_
 #define MOCKTAIL_RUNTIME_GRAPHICS_LAUNCH_POLICY_H_
 
+#include <filesystem>
 #include <string>
+#include <string_view>
+#include <vector>
 
 #include "runtime/runtime_config.h"
 
 namespace mocktail {
 namespace runtime {
 
+// Readable ICD manifest for `vendor` that this build can actually load, or an
+// empty path. Directories are searched in order; a manifest built for another
+// architecture is never selected.
+std::string SelectVulkanIcdManifest(
+    const std::vector<std::filesystem::path>& directories,
+    std::string_view vendor);
+
 // Publishes the resolved graphics backend before the managed payload updater
 // starts. OpenGL is a strict system EGL/GLES path; it never silently retries
 // through ANGLE/Vulkan or accepts a window without a real graphics context.