meta-rust-bin prepends itself to BBPATH

[taamrooz]

I noticed this while trying to mitigate #204. The current conf/layer.conf has the following line:

BBPATH =. "${LAYERDIR}:"

According to the BitBake documentation =. means to prepend a string without a space. Meaning that meta-rust-bin puts itself in front of other layers, even though the user may have ordered these layers differently.

Yocto still has no proper mechanism to patch/override .bbclass files, so we're stuck having to create a layer and put it at the top of bblayers.conf. https://yocto.yoctoproject.narkive.com/qcV9UXm4/overriding-a-class-in-custom-layer

Looking at previous issues, this seems to have been done in order to get things working for Honister: #108. #123

Would it be possible to change things back to the default BitBake has for layer.conf files?

BBPATH .= ":${LAYERDIR}"

https://docs.yoctoproject.org/5.1.2/bsp-guide/bsp.html#layer-configuration-file