Add build.config

Bug: 19677119
Change-Id: I327eb4c242bbdf3065799078d6a506cabbfb331f

build.config

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