ANDROID: build.config: Set DTC to absolute path

The device tree compiler specified by $(DTC) is actually used as a
prerequisite for the following .dtb makefile rule:

$(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE

Ensure that it's set to an absolute path so that make can actually find
it. Otherwise, make will not instantiate that rule, because it can't
find dtc.

Bug: 198176779
Fixes: 023411c ("ANDROID: Use DTC from the hermetic toolchain")
Signed-off-by: Daniel Mentz <[email protected]>
Change-Id: I4e190192b39c4cf18c6412cc85895ed1ce2ec6dd

Author: danielmentzgoogle

build.config.common

@@ -3,9 +3,9 @@ KMI_GENERATION=0
 
 LLVM=1
 DEPMOD=depmod
-DTC=dtc
 CLANG_PREBUILT_BIN=prebuilts/clang/host/linux-x86/clang-r433403/bin
 BUILDTOOLS_PREBUILT_BIN=build/build-tools/path/linux-x86
+DTC=${ROOT_DIR}/${BUILDTOOLS_PREBUILT_BIN}/dtc
 
 EXTRA_CMDS=''
 STOP_SHIP_TRACEPRINTK=1