doc: "Variable ZEPHYR_TOOLCHAIN_VARIANT is not defined"

[andrewboie]

Describe the bug
Imaged a new Ubuntu machine and followed all the directions on https://docs.zephyrproject.org/latest/getting_started/index.html

I used the default location for the SDK.

Unfortunately, this page doesn't mention that ZEPHYR_TOOLCHAIN_VARIANT has to be set for twister to work.

To Reproduce

andrew@meatwad:~/projects/zephyr/zephyr$  twister -p qemu_x86
Renaming output directory to /home/andrew/projects/zephyr/zephyr/twister-out.1
INFO    - Zephyr version: zephyr-v2.4.0-2399-g7883eedfde
INFO    - JOBS: 32
E: Variable ZEPHYR_TOOLCHAIN_VARIANT is not defined

Expected behavior
Doc page would mention this detail.

Impact
Minor

[SeppoTakalo]

I was just searching for the same issue.
Apparently export ZEPHYR_TOOLCHAIN_VARIANT=zephyr is the right choice, if you installed the Zephyr SDK, and it has been visible in the documentation in the past:
https://docs.zephyrproject.org/1.14.1/getting_started/installation_linux.html#zephyr-sdk

But current documentation does not mention it. Probably at some point all the build tools detected Zephyr SDK automatically, so they removed the mention about setting that variable.

[tejlmand]

Probably at some point all the build tools detected Zephyr SDK automatically, so they removed the mention about setting that variable.

Correct. CMake handles this automatically when using newer Zephyr SDK's. (from 0.11.3 and beyond).

This issue is related to running twister, which seems to also test for the Toolchain variable, so i'm looking into aligning code so this can be done in a single place.
See also:
https://github.com/zephyrproject-rtos/zephyr/pull/31936/files#r570036292

[tejlmand]

if trying to build using west or CMake / Ninja, then you should not see this issue.

[SeppoTakalo]

west+CMake+Ninja works OK, as expected.
This issue is only within Twister.