Add build.config

Bug: 19661035
Change-Id: If8a4421c3258f95a977128ea3489a1cea9b5f31d

build.config

+ARCH=arm
+BRANCH=android-msm-hammerhead-3.4-lmp-mr1
+CROSS_COMPILE=arm-eabi-
+DEFCONFIG=hammerhead_defconfig
+EXTRA_CMDS=''
+KERNEL_DIR=private/msm-lge
+LINUX_GCC_CROSS_COMPILE_PREBUILTS_BIN=prebuilts/gcc/linux-x86/arm/arm-eabi-4.8/bin
+FILES="
+arch/arm/boot/zImage-dtb
+vmlinux
+System.map
+"