kernel: Remove ANDROID_BUILD_TOP

This is no longer used in Pie, so just get the top dir of the build system
and use that.

Change-Id: I4bc416e471ddeb9810960f4ddcd647b20aa531c2

build/tasks/kernel.mk

@@ -230,15 +230,17 @@ KERNEL_TOOLCHAIN_PATH := $(KERNEL_TOOLCHAIN)/$(KERNEL_TOOLCHAIN_PREFIX)
 endif
 endif
 
+BUILD_TOP := $(shell pwd)
+
 ifeq ($(TARGET_KERNEL_CLANG_COMPILE),true)
     ifneq ($(TARGET_KERNEL_CLANG_VERSION),)
         # Find the clang-* directory containing the specified version
-        KERNEL_CLANG_VERSION := $(shell find $(ANDROID_BUILD_TOP)/prebuilts/clang/host/$(HOST_OS)-x86/ -name AndroidVersion.txt -exec grep -l $(TARGET_KERNEL_CLANG_VERSION) "{}" \; | sed -e 's|/AndroidVersion.txt$$||g;s|^.*/||g')
+        KERNEL_CLANG_VERSION := $(shell find $(BUILD_TOP)/prebuilts/clang/host/$(HOST_OS)-x86/ -name AndroidVersion.txt -exec grep -l $(TARGET_KERNEL_CLANG_VERSION) "{}" \; | sed -e 's|/AndroidVersion.txt$$||g;s|^.*/||g')
     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 ?= $(ANDROID_BUILD_TOP)/prebuilts/clang/host/$(HOST_OS)-x86/$(KERNEL_CLANG_VERSION)/bin
+    TARGET_KERNEL_CLANG_PATH ?= $(BUILD_TOP)/prebuilts/clang/host/$(HOST_OS)-x86/$(KERNEL_CLANG_VERSION)/bin
     ifeq ($(KERNEL_ARCH),arm64)
         KERNEL_CLANG_TRIPLE ?= CLANG_TRIPLE=aarch64-linux-gnu-
     else ifeq ($(KERNEL_ARCH),arm)
@@ -253,7 +255,7 @@ ifneq ($(USE_CCACHE),)
     ccache := $(shell which ccache)
 
     ifeq ($(ccache),)
-        ccache := $(ANDROID_BUILD_TOP)/prebuilts/misc/$(HOST_PREBUILT_TAG)/ccache/ccache
+        ccache := $(BUILD_TOP)/prebuilts/misc/$(HOST_PREBUILT_TAG)/ccache/ccache
         # Check that the executable is here.
         ccache := $(strip $(wildcard $(ccache)))
     endif
@@ -270,7 +272,7 @@ endif
 ccache =
 
 ifeq ($(HOST_OS),darwin)
-  MAKE_FLAGS += C_INCLUDE_PATH=$(ANDROID_BUILD_TOP)/external/elfutils/libelf:/usr/local/opt/openssl/include
+  MAKE_FLAGS += C_INCLUDE_PATH=$(BUILD_TOP)/external/elfutils/libelf:/usr/local/opt/openssl/include
   MAKE_FLAGS += LIBRARY_PATH=/usr/local/opt/openssl/lib
 endif