ANDROID: move CLANG_VERSION definition to build.config.constants

Moving this static value to a separate configuration file allows it to
be used from other builds as well, such as the Kleaf build.

Bug: 210296725
Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: I07aac5609d8ec986e0e270fdbba3662ac10029f4

build.config.common

@@ -1,9 +1,11 @@
+. ${ROOT_DIR}/${KERNEL_DIR}/build.config.constants
+
 BRANCH=android-mainline
 KMI_GENERATION=0
 
 LLVM=1
 DEPMOD=depmod
-CLANG_PREBUILT_BIN=prebuilts/clang/host/linux-x86/clang-r437112/bin
+CLANG_PREBUILT_BIN=prebuilts/clang/host/linux-x86/clang-${CLANG_VERSION}/bin
 BUILDTOOLS_PREBUILT_BIN=build/build-tools/path/linux-x86
 DTC=${ROOT_DIR}/${BUILDTOOLS_PREBUILT_BIN}/dtc
 

build.config.constants

@@ -0,0 +1 @@
+CLANG_VERSION=r437112