kernel: Conditionally use dtc from prebuilt

Change-Id: I1c3a2ae03b8cbe2a32e0ca72aeb7a15de2a397e3
diff --git a/build/tasks/kernel.mk b/build/tasks/kernel.mk
index e40bb9e..bab79eb 100644
--- a/build/tasks/kernel.mk
+++ b/build/tasks/kernel.mk
@@ -204,9 +204,15 @@
 # Internal implementation of make-kernel-target
 # $(1): output path (The value passed to O=)
 # $(2): target to build (eg. defconfig, modules, dtbo.img)
-define internal-make-kernel-target
-$(PATH_OVERRIDE) $(KERNEL_MAKE_CMD) $(KERNEL_MAKE_FLAGS) -C $(KERNEL_SRC) O=$(KERNEL_BUILD_OUT_PREFIX)$(1) DTC=$(KERNEL_DTC_CMD) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) $(KERNEL_CLANG_TRIPLE) $(KERNEL_CC) $(KERNEL_LD) $(2)
-endef
+ifeq ($(TARGET_USES_PREBUILT_DTC),true)
+    define internal-make-kernel-target
+    $(PATH_OVERRIDE) $(KERNEL_MAKE_CMD) $(KERNEL_MAKE_FLAGS) -C $(KERNEL_SRC) O=$(KERNEL_BUILD_OUT_PREFIX)$(1) DTC=$(KERNEL_DTC_CMD) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) $(KERNEL_CLANG_TRIPLE) $(KERNEL_CC) $(KERNEL_LD) $(2)
+    endef
+else
+    define internal-make-kernel-target
+    $(PATH_OVERRIDE) $(KERNEL_MAKE_CMD) $(KERNEL_MAKE_FLAGS) -C $(KERNEL_SRC) O=$(KERNEL_BUILD_OUT_PREFIX)$(1) ARCH=$(KERNEL_ARCH) $(KERNEL_CROSS_COMPILE) $(KERNEL_CLANG_TRIPLE) $(KERNEL_CC) $(KERNEL_LD) $(2)
+    endef
+endif
 
 # Make a kernel target
 # $(1): The kernel target to build (eg. defconfig, modules, modules_install)