ANDROID: Move BRANCH from build.config.common to .constants.

This allows Bazel to load the value of $BRANCH in order
to determine the value of --dist_dir of copy_to_dist_dir
statically.

Test: TH
Bug: 229268271

Change-Id: Iff759b8188360ea1b2bc204d29750eece9095582
Signed-off-by: Yifan Hong <elsk@google.com>

build.config.common

@@ -1,6 +1,5 @@
 . ${ROOT_DIR}/${KERNEL_DIR}/build.config.constants
 
-BRANCH=android13-5.10
 KMI_GENERATION=3
 
 LLVM=1

build.config.constants

@@ -1 +1,2 @@
+BRANCH=android13-5.10
 CLANG_VERSION=r450784b