New variable added here, if I understood correctly: https://lists.openembedded.org/g/openembedded-core/message/154304
... unlike the TOOLCHAIN_HOST_TASK and TOOLCHAIN_TARGET_TASK variables that are already documented.
Needs a note in the migration guide.
A note was added to the migration guide (thanks to Paul Eggelton). Documentation for this variable was proposed: https://lists.yoctoproject.org/g/docs/message/2003
Fixed by this commit: http://git.yoctoproject.org/cgit/cgit.cgi/yocto-docs/commit/?id=2adac164a2d4cf23c0372c1154709f2866d483fa
Closing the bug