ANDROID: Specify MAKE_GOALS and optimize targets

The default goals for an ARCH=arm64 kernel will build all of the dtb
files available in the tree, and hard-codes the generation of a
gzip-compressed Image artifact. For GKI, we want to support various
compression methods (gz, lz4 and uncompressed) and this can be handled
outside of kbuild where compressor flags can be tuned. Also, GKI does
not need to build any dtb files because it is board-neutral, and in most
cases the dtbs will come from downstream kernels, not ACK.

On arm and aarch64, this suppresses the generation of the useless gzip
compressed Image artifact, and dtbs on the gki configs, which do not make
sense. The x86 defaults were already optimal but make them match
aarch64. On db845c, this builds only the needed dtb file and a compressed
artifact for backwards compatibility.

Bug: 152546767
Change-Id: If90ea331fc7564358b77a777fb367d7d2f95e6a6
Signed-off-by: Alistair Delva <adelva@google.com>
diff --git a/build.config.arm b/build.config.arm
index 8eb547e..7f71449 100644
--- a/build.config.arm
+++ b/build.config.arm
@@ -4,8 +4,12 @@
 CROSS_COMPILE=arm-linux-androidkernel-
 LINUX_GCC_CROSS_COMPILE_PREBUILTS_BIN=prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9/bin
 
+MAKE_GOALS="
+Image
+modules
+"
+
 FILES="
-arch/arm/boot/Image.gz
 arch/arm/boot/Image
 vmlinux
 System.map