raviole: Pull init.insmod.*.cfg from vendor_dlkm

We've started pushing init.insmod.*.cfg into the kernel prebuilts, and
installing it to /vendor_dlkm/etc, but it may not be available on all
prebuilt variants (e.g., kernel 5.10).

Here, we:
1. conditionally install our common init.*cfg to /vendor_dlkm (only if
   $(TARGET_KERNEL_DIR) doesn't have a copy)
2. point init at /vendor_dlkm/etc

When we've cycled completely off of kernel 5.10, we can drop #1.

Bug: 369686096
Test: build, boot
Flag: EXEMPT refactor
Change-Id: Ibefafbcfe1fdf9b4e65ee3d73126c33f04ee193b
diff --git a/device-slider.mk b/device-slider.mk
index e49b151..5e90e1a 100644
--- a/device-slider.mk
+++ b/device-slider.mk
@@ -48,9 +48,13 @@
 PRODUCT_COPY_FILES += \
 	device/google/gs101/conf/init.recovery.device.rc:$(TARGET_COPY_OUT_RECOVERY)/root/init.recovery.slider.rc
 
-# insmod files
+# insmod files. Kernel 5.10 prebuilts don't provide these yet, so provide our
+# own copy if they're not in the prebuilts.
+# TODO(b/369686096): drop this when 5.10 is gone.
+ifeq ($(wildcard $(TARGET_KERNEL_DIR)/init.insmod.*.cfg),)
 PRODUCT_COPY_FILES += \
-	device/google/raviole/init.insmod.slider.cfg:$(TARGET_COPY_OUT_VENDOR)/etc/init.insmod.slider.cfg
+	device/google/raviole/init.insmod.slider.cfg:$(TARGET_COPY_OUT_VENDOR_DLKM)/etc/init.insmod.slider.cfg
+endif
 
 # Thermal Config
 PRODUCT_COPY_FILES += \