Error building CM13 for Sony Xperia V (libta) - Android Q&A, Help & Troubleshooting

Hi there.
I recently decided to try getting some more fun out of my old (by today's standards, grmbl) Xperia V by upgrading to a newer Android version. So I grabbed a Cyanogenmod 13 nightly and managed to get it all set up, and I'm quite happy about it. However, I ran into an issue with feedback when activating speakerphone. There is a bug report for this issue already, but I cannot link to it because I am a new forum user... it's in the Cyanogenmod Jira and has the ID "CYAN-2110". It's for a different phone but it's the same hardware platform.
Apparently nobody ever fixed this properly by making the device use the correct mic in speakerphone mode, so I decided to jump in and try fixing it myself.
However, for now I am stuck because my CM13 build does not work yet. I followed the build instructions in the guide on the Cyanogenmod wiki on the page "Build_for_tsubasa", except that I ran ./extract-files.sh in ~/android/system/device/sony/blue-common as well as in tsubasa, otherwise breakfast would complain.
After that I managed to start a build which ran for ~15 minutes and compiled a good lot of stuff before erroring out like so:
Code:
make: *** Keine Regel vorhanden, um das Ziel „/home/simmax/android/system/out/target/product/tsubasa/obj/SHARED_LIBRARIES/libta_intermediates/export_includes“,
benötigt von „/home/simmax/android/system/out/target/product/tsubasa/obj/EXECUTABLES/macaddrsetup_intermediates/import_includes“, zu erstellen. Schluss.
make: *** Auf noch nicht beendete Prozesse wird gewartet …
target thumb C: linker <= bionic/linker/linker_libc_support.c
make: Verzeichnis „/home/simmax/android/system“ wird verlassen
#### make failed to build some targets (16:57 (mm:ss)) ####
In case your German is rusty, it says that make was unable to find a rule for building „/home/simmax/android/system/out/target/product/tsubasa/obj/SHARED_LIBRARIES/libta_intermediates/export_includes“ which is needed by „/home/simmax/android/system/out/target/product/tsubasa/obj/EXECUTABLES/macaddrsetup_intermediates/import_includes“.
libta.so appears to be one of the libraries that ./extract-files.sh copied from the phone. It seems to have been copied correctly and is sitting in android/system/vendor/sony/blue-common/proprietary/lib.
I already asked about it on #cyanogenmod-dev, and was told that "copying is not enough, macaddrsetup is trying to link against it so you also need to add it as a shared prebuilt library". Unfortunately the user who provided this insight didn't answer my follow-up question, so this does not really help me because I have no real idea how the build environment works and how to implement his suggestion. Maybe it helps you help me though...

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Following up on this:
The issue is that the ./extract-files.sh in devices/sony/blue-common does not create an Android.mk file which is needed for a few of the libraries which it copies. This can be fixed by going the same way as the android_device_sony_huashan repository, by providing a platform-specific ./setup-makefiles.sh which is called from ./extract-files.sh. I did that and am going to make a pull request to the blue-common repo, so that this can be fixed for everyone.
Another part I got stuck on was a series of messages when running ./extract-files.sh, implying that some files it needed were not present on my phone. The real issue was that adb needs root access to pull these files, so it needs to be activated in the developer settings on the phone *and* you need to run "adb root" on the shell of your build machine before running ./extract-files.sh.
The last remaining issue that stands in the way of making a build according to the official script is that there is still a missing proprietary blob (boot/RPM.bin). I assume this also needs to be extracted from the phone somehow, but I am not sure how to make that happen yet.