ANDROID: refactor build.config files to remove duplication

The build.config.* files largely contain duplicate information by their
nature. Reorganize them reduce duplication and to allow adding new
configurations without copying the definitions again.

Bug: 140224784
Change-Id: I6a3810a125b0ed48591690ca33bb5c02be58218a
Signed-off-by: Matthias Maennich <maennich@google.com>
(cherry picked from commit 7d642373db4c6c1c6ed8af02492047896beb4a47)
diff --git a/build.config.common b/build.config.common
new file mode 100644
index 0000000..d5b188f
--- /dev/null
+++ b/build.config.common
@@ -0,0 +1,8 @@
+BRANCH=android-4.9-q
+KERNEL_DIR=common
+
+CC=clang
+CLANG_PREBUILT_BIN=prebuilts-master/clang/host/linux-x86/clang-r353983c/bin
+
+EXTRA_CMDS=''
+STOP_SHIP_TRACEPRINTK=1