Using INITRAMFS_MULTICONFIG breaks the build and produces a stack trace from bitbake. The simpler way to reproduce the issue is to set INITRAMFS_MULTICONFIG = "default" (which doesn't require one to create a multiconfig entry nor changing TMPDIR) and bitbake will output something similar to this: http://ix.io/4g8T
https://git.yoctoproject.org/poky/commit/bitbake?id=70a7e7337bb62bc511972f710fd56a5ac627c8cc