When sourcing conf/setenv the below snippet searches all your layers for a scripts directory and adds it to your path.

# check for any scripts directories in the top-level of the repos and add those
# to the PATH
SCRIPTS=`find ${OEBASE}/sources -maxdepth 2 -name "scripts" -type d`
for s in ${SCRIPTS}
do
    PATH="${s}:$PATH"
done

Usually oe-core is the only layer that contains a scripts directory but it is possible for other layers to define their own especially if they plan on overriding a script contained within oe-core's scripts directory.

oe-core/scripts/bitbake contains the below snippet:

export PATH=`echo $PATH | sed s#[^:]*/scripts:##`

This portion is meant to remove any scripts directory from the PATH temporarily. However, this assumes that only one scripts directory has been defined. In the event that more scripts directory is located in the path only once instance will be removed. For whatever reason the bitbake script freaks out and results in a recursive call to itself spawning multiple instances of itself until after a long time it crashes.

The simple fix is to add the g option to the regular expression so all instances of the scripts directory within the path is removed.