android/filesystems/ramdisk_extractor.h: new file.

This patch introduces a new function that can be used to
extract single data file content from an Android ramdisk.img
image.

This will be used to extract fstab.goldfish in a future patch
to reliably determine the format of each partition image before
the emulator is run.

Change-Id: I4e8178ce1cedf0e93b852c632003d089bcd41701
diff --git a/Makefile.common b/Makefile.common
index 17f886e..6d8fcca 100644
--- a/Makefile.common
+++ b/Makefile.common
@@ -124,6 +124,7 @@
 	android/emulation/CpuAccelerator.cpp \
 	android/filesystems/ext4_utils.cpp \
 	android/filesystems/partition_types.cpp \
+	android/filesystems/ramdisk_extractor.cpp \
 	android/kernel/kernel_utils.cpp \
 	android/utils/assert.c \
 	android/utils/bufprint.c \