build-configs.yaml: add x86 DRM fragment

Add a new fragment for x86 DRM testing, including the necessary
configuration for VKMS testing.

Signed-off-by: Vignesh Raman <vignesh.raman@collabora.com>

Author: vigneshraman

config/core/build-configs.yaml

@@ -1001,6 +1001,11 @@ fragments:
       iwlwifi-9000-pu-b0-jf-b0-46.ucode
       "'
 
+  x86-drm:
+    path: "kernel/configs/x86-board.config"
+    configs:
+      - 'CONFIG_DRM_VKMS=m'
+
   x86_kvm_guest:
     path: "kernel/configs/kvm_guest.config"