emulator: package ramdisk-qemu.img to image zip

BUG: 149826779
Test: build
Change-Id: I7949daa15edafeeb51e80d320bcbb5a450cd0a49
diff --git a/build/sdk.atree b/build/sdk.atree
index f4038aa..9ea4040 100644
--- a/build/sdk.atree
+++ b/build/sdk.atree
@@ -240,7 +240,7 @@
 # System images + Kernel
 system-qemu.img                                 system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/system.img
 vendor-qemu.img                                 system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/vendor.img
-ramdisk.img                                system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/ramdisk.img
+ramdisk-qemu.img                                system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/ramdisk.img
 device/generic/goldfish/data/etc/userdata.img    system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/userdata.img
 data/misc                                        system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/data/misc
 system/build.prop                          system-images/${PLATFORM_NAME}/${TARGET_CPU_ABI}/build.prop