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.aarch64 b/build.config.aarch64
new file mode 100644
index 0000000..523bbc0
--- /dev/null
+++ b/build.config.aarch64
@@ -0,0 +1,11 @@
+ARCH=arm64
+
+CLANG_TRIPLE=aarch64-linux-gnu-
+CROSS_COMPILE=aarch64-linux-androidkernel-
+LINUX_GCC_CROSS_COMPILE_PREBUILTS_BIN=prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin
+
+FILES="
+arch/arm64/boot/Image.gz
+vmlinux
+System.map
+"