kernel: Fix clang version override

Change-Id: I18fceeeeab5426f55a73d0cb8d72abd5f40c67ec
diff --git a/config/BoardConfigKernel.mk b/config/BoardConfigKernel.mk
index a85737e..21d5e08 100644
--- a/config/BoardConfigKernel.mk
+++ b/config/BoardConfigKernel.mk
@@ -27,6 +27,8 @@
 #                                                      x86_64-linux-androidkernel- for x86
 #
 #   TARGET_KERNEL_CLANG_COMPILE        = Compile kernel with clang, defaults to false
+#   TARGET_KERNEL_CLANG_VERSION        = Clang prebuilts version, optional, defaults to clang-stable
+#   TARGET_KERNEL_CLANG_PATH           = Clang prebuilts path, optional
 #
 #   KERNEL_TOOLCHAIN_PREFIX            = Overrides TARGET_KERNEL_CROSS_COMPILE_PREFIX,
 #                                          Set this var in shell to override
@@ -51,10 +53,14 @@
 KERNEL_ARCH := $(TARGET_KERNEL_ARCH)
 endif
 
-LLVM_RELEASE_VERSION ?= 18
-LLVM_PREBUILTS_VERSION ?= clang-r510928
+ifneq ($(TARGET_KERNEL_CLANG_VERSION),)
+    KERNEL_CLANG_VERSION := clang-$(TARGET_KERNEL_CLANG_VERSION)
+else
+    # Use the default version of clang if TARGET_KERNEL_CLANG_VERSION hasn't been set by the device config
+    KERNEL_CLANG_VERSION := $(LLVM_PREBUILTS_VERSION)
+endif
+TARGET_KERNEL_CLANG_PATH ?= $(BUILD_TOP)/prebuilts/clang/host/$(HOST_PREBUILT_TAG)/$(KERNEL_CLANG_VERSION)
 
-CLANG_PREBUILTS := $(BUILD_TOP)/prebuilts/clang/host/$(HOST_PREBUILT_TAG)/$(LLVM_PREBUILTS_VERSION)
 GCC_PREBUILTS := $(BUILD_TOP)/prebuilts/gcc/$(HOST_PREBUILT_TAG)
 # arm64 toolchain
 KERNEL_TOOLCHAIN_arm64 := $(GCC_PREBUILTS)/aarch64/aarch64-linux-android-4.9/bin
@@ -133,8 +139,8 @@
 KERNEL_MAKE_CMD := $(BUILD_TOP)/prebuilts/build-tools/$(HOST_PREBUILT_TAG)/bin/make
 
 # Set the full path to the clang command
-KERNEL_MAKE_FLAGS += HOSTCC=$(CLANG_PREBUILTS)/bin/clang
-KERNEL_MAKE_FLAGS += HOSTCXX=$(CLANG_PREBUILTS)/bin/clang++
+KERNEL_MAKE_FLAGS += HOSTCC=$(TARGET_KERNEL_CLANG_PATH)/bin/clang
+KERNEL_MAKE_FLAGS += HOSTCXX=$(TARGET_KERNEL_CLANG_PATH)/bin/clang++
 
 # Since Linux 4.16, flex and bison are required
 KERNEL_MAKE_FLAGS += LEX=$(BUILD_TOP)/prebuilts/build-tools/$(HOST_PREBUILT_TAG)/bin/flex