[E 2015 Original Android Development] squid2:
CM13 Progress

I now have it partially booting (up to the boot animation) when using a special hand-modified boot image (CM12.1 ramdisk with CM13 init scripts). It's currently getting stuck on some Java errors involving com.android.okhttp

02-18 04:22:06.313 1709 1709 E dex2oat : Unexpected failure to resolve a method: void com.android.okhttp.TcmIdleTimerMonitor.<clinit>()
02-18 04:22:06.313 1709 1709 F dex2oat : art/compiler/oat_writer.cc:627] java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack trace available
02-18 04:22:06.313 1709 1709 F dex2oat : art/compiler/oat_writer.cc:627] (Throwable with empty stack trace)
02-18 04:22:06.329 1709 1709 F dex2oat : art/runtime/barrier.cc:90] Check failed: count_ == 0 (count_=-1, 0=0) Attempted to destroy barrier with non zero count
02-18 04:22:06.329 1709 1709 F dex2oat : art/runtime/runtime.cc:366] Runtime aborting --- recursively, so no thread-specific detail!
02-18 04:22:06.329 1709 1709 F dex2oat : art/runtime/runtime.cc:366]
02-18 04:22:06.329 1709 1709 F libc : Fatal signal 6 (SIGABRT), code -6 in tid 1709 (main)

...

02-18 04:22:06.555 1550 1550 E art : Could not create image space with image file '/system/framework/boot.art'. Attempting to fall back to imageless running. Error was: Failed to generate image '/data/dalvik-cache/arm/system@framework@boot.art': Failed execv(/system/bin/dex2oat --image=/data/dalvik-cache/arm/system@framework@boot.art --dex-file=/system/framework/core-libart.jar --dex-file=/system/framework/conscrypt.jar --dex-file=/system/framework/okhttp.jar --dex-file=/system/framework/core-junit.jar --dex-file=/system/framework/bouncycastle.jar --dex-file=/system/framework/ext.jar --dex-file=/system/framework/framework.jar --dex-file=/system/framework/telephony-common.jar --dex-file=/system/framework/voip-common.jar --dex-file=/system/framework/ims-common.jar --dex-file=/system/framework/apache-xml.jar --dex-file=/system/framework/org.apache.http.legacy.boot.jar --oat-file=/data/dalvik-cache/arm/system@framework@boot.oat --instruction-set=arm --instruction-set-features=smp,div,-atomic_ldrd_strd --base=0x70dd1000 --runtime-arg -Xms64m --runti

02-18 04:22:15.908 1550 1550 I art : Rejecting re-init on previously-failed class java.lang.Class<com.android.okhttp.TcmIdleTimerMonitor>
02-18 04:22:15.914 1550 1550 E Zygote : Error preloading com.android.okhttp.ConnectionPool.
02-18 04:22:15.914 1550 1550 E Zygote : java.lang.NoClassDefFoundError: com.android.okhttp.TcmIdleTimerMonitor
02-18 04:22:15.914 1550 1550 E Zygote : at com.android.okhttp.ConnectionPool.<init>(ConnectionPool.java:105)
02-18 04:22:15.914 1550 1550 E Zygote : at com.android.okhttp.ConnectionPool.<clinit>(ConnectionPool.java:71)
02-18 04:22:15.914 1550 1550 E Zygote : at java.lang.Class.classForName(Native Method)
02-18 04:22:15.914 1550 1550 E Zygote : at java.lang.Class.forName(Class.java:324)
02-18 04:22:15.914 1550 1550 E Zygote : at com.android.internal.os.ZygoteInit.preloadClasses(ZygoteInit.java:277)
02-18 04:22:15.914 1550 1550 E Zygote : at com.android.internal.os.ZygoteInit.preload(ZygoteInit.java:182)
02-18 04:22:15.914 1550 1550 E Zygote : at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)

If anyone wants to play with it and try to make it go further, here are my CM13 interim hacked build instructions and here is my hacked boot image.