Issue while repacking Lollipop system.img

I want to make some changes in the system.img and flash it into my Nexus 5.

To modify the .img I first need to unpack it into filesystem, make the changes and then repack into new system.img.

I'm following a guide for unpack/repack system.img. This is my first post so not allowed to link the URL of guide, but you can search for "muzso.hu How to pack and unpack system.img and userdata.img from an Android factory image"

Steps I'm taking:

I. Clone ASOP scripts:

Code:

---

    git clone https://android.googlesource.com/platform/system/extras
    git clone https://android.googlesource.com/platform/external/libselinux/
    git clone https://android.googlesource.com/platform/system/core/

---

II. Checkout specific version:

Code:

---

    cd extras
    git checkout android-5.1.1_r9

---

III. Compiling c files to create make_ext4fs (which is used to repack the filesystem into img)

Code:

---

    cd ..
    gcc -o make_ext4fs -Icore/libsparse/include -Ilibselinux/include -Icore/include -lz extras/ext4_utils/canned_fs_config.c extras/ext4_utils/make_ext4fs_main.c extras/ext4_utils/make_ext4fs.c extras/ext4_utils/ext4fixup.c extras/ext4_utils/ext4_utils.c extras/ext4_utils/allocate.c extras/ext4_utils/contents.c extras/ext4_utils/extent.c extras/ext4_utils/indirect.c extras/ext4_utils/uuid.c extras/ext4_utils/sha1.c extras/ext4_utils/wipe.c core/libsparse/backed_block.c core/libsparse/output_file.c core/libsparse/sparse.c core/libsparse/sparse_crc32.c core/libsparse/sparse_err.c core/libsparse/sparse_read.c

---

But above command is giving me error:

Code:

---

extras/ext4_utils/make_ext4fs_main.c: In function ‘main’:
extras/ext4_utils/make_ext4fs_main.c:187:20: error: ‘fs_config’ undeclared (first use in this function)
  fs_config_func = fs_config;
                    ^
extras/ext4_utils/make_ext4fs_main.c:187:20: note: each undeclared identifier is reported only once for each function it appears in

---

It says fs_config in undeclared. But this is ASOP code, provided by Android only.

What am I missing..?

I think I've included all the header files, but now I'm not sure.

Please help. This is very frustrating.

I will be very thankful, if someone can please post the guide on how to unpack & repack for android-5.1.1_r9. Because all the guides available on net are for previous versions & now ASOP files have been changed.

P.S. - I'm a noob in C. So great help if anyone can explain in simple terms.

Thank You